I doubt you will damage anything replacing the hard drive most laptop have it behind one of the access panel on bottom 2 mins job for most laptops.
The parts replacement you can break it if not careful are generally the ones you need to remove the motherboard etc like replacing CPU cooler etc.
Thanks 
Add SSD & install your OS on it. Trust me this is the only possible solution, rest just want to play with you and are fooling you 
nah
just taking away some tech anxiety
replacing SSD and installing lightweight Linux is easy, cleaning the ducts, blower and checking and replacing cooling paste just makes it perform a lot better and needs more effort.
Will that MX ssd fit or should I double check?
It’ll fit, it’s just regular SATA if it’s 5 years old. If you want to make sure, just Google your notebook type + SSD.
Change the SSHD to a SSD
Check temperatures to make sure the CPU/GPU isnt throttling
2.1) If so, open the laptop and change the termal paste to something like artic silver 5, MX-4, MX-2 or noctua nt-h1
2.2) If the cpu continues hot, try to undervolt it (watch this video for more info, $12 Hack To Boost Your Laptop Performance! - YouTube)
2.3) Make sure that there isn’t any dead fan
Reinstall the OS
That shit still exists? I remember paying like $10 for a tube of that for my AMD nuclear weapon Athlon. It did help cool like 2c more than the stock free shit, but that’s like throwing an ice cube at the sun.
SSHD access going very far south probably means that the NAND is having issues, and it’s gone to “oh shit” territory. The bad news- you can’t use SMART to get useful data because it uses the ‘bad reads’ counter for cache failures (at least Seagate does).
FWIW, I bought NOS not all that long ago.
SMART Attributes Data Structure revision number: 10
Vendor Specific SMART Attributes with Thresholds:
ID# ATTRIBUTE_NAME FLAG VALUE WORST THRESH TYPE UPDATED WHEN_FAILED RAW_VALUE
1 Raw_Read_Error_Rate 0x000f 118 100 006 Pre-fail Always - 181009304
3 Spin_Up_Time 0x0003 098 098 000 Pre-fail Always - 0
4 Start_Stop_Count 0x0032 100 100 020 Old_age Always - 58
5 Reallocated_Sector_Ct 0x0033 100 100 010 Pre-fail Always - 0
7 Seek_Error_Rate 0x000f 069 060 030 Pre-fail Always - 4304777888
9 Power_On_Hours 0x0032 099 099 000 Old_age Always - 1593
10 Spin_Retry_Count 0x0013 100 100 097 Pre-fail Always - 0
12 Power_Cycle_Count 0x0032 100 100 020 Old_age Always - 63
184 End-to-End_Error 0x0032 100 100 099 Old_age Always - 0
187 Reported_Uncorrect 0x0032 100 100 000 Old_age Always - 0
188 Command_Timeout 0x0032 100 100 000 Old_age Always - 0
189 High_Fly_Writes 0x003a 100 100 000 Old_age Always - 0
190 Airflow_Temperature_Cel 0x0022 066 060 045 Old_age Always - 34 (Min/Max 18/36)
191 G-Sense_Error_Rate 0x0032 100 100 000 Old_age Always - 0
192 Power-Off_Retract_Count 0x0032 100 100 000 Old_age Always - 1
193 Load_Cycle_Count 0x0032 093 093 000 Old_age Always - 14943
194 Temperature_Celsius 0x0022 034 040 000 Old_age Always - 34 (0 16 0 0 0)
197 Current_Pending_Sector 0x0012 100 100 000 Old_age Always - 0
198 Offline_Uncorrectable 0x0010 100 100 000 Old_age Offline - 0
199 UDMA_CRC_Error_Count 0x003e 200 200 000 Old_age Always - 0
254 Free_Fall_Sensor 0x0032 100 100 000 Old_age Always - 0
It depends on the quality of his current paste. I repasted my gf’s old laptop, the cpu was one of those old t4200 Pentiums, it was running at 75C 'ish. After applying new paste it went down to 40 something. But at that point the paste wasn’t even paste, it was solid and looked like tiny rocks.
Since OP said that the laptop is old it may just be shitty paste that is causing the CPU to overheat and then throttle, that can be confirmed with any temperature monitoring software
I think the point that @WSS was trying to convey is that expensive thermal paste makes a minor difference in comparison to cheaper thermal paste.
Yes, that is true for the temperature. But I’m not sure about longevity.
At this point any new fresh paste is better than the one he has inside his laptop right now
Much as breathing water isn’t good for electronic things.
Updating the paste may cool it down, but we don’t even know if it’s overheating. This can be a rather time consuming task - and is NOT a task for someone who has never opened their laptop before.
To use a car analogy- the first time you change oil, it’s empowering. You don’t start off with an engine swap, unless you’ve got a hell of a good mentor.
Baby steps. Baby steps.
Someone should make a tech/electric DIY thread. Could post some pics of Xbox Original mods I did a while back. I’m sure lots of members have interesting stuff they’ve worked on.
I think I don’t just pay for performance when I get Arctic Silver 5 or MX-5 (which are both actually quite cheap nowadays and you get build a stockpile whenever you buy parts that include them) but also how easy it is to apply, remove/clean, etc. Anyway if you’re going to repaste you might as well get the nice stuff, it’s like skimping on a PSU… no point. Also, you could get the new graphite pads (solid pads, can reuse hundreds of times!) if you like.
To be fair, if it’s really old and depending on how it has been ran (it’s a laptop so likely on/off constantly, which dries out paste faster), it could literally be a solid right now that is exchanging barely any heat. I saw that in like 4/5 of the 10 year old Xbox’s I pulled apart.
I bought a 65g syringe of MX-2 like 10 years ago. Still use the same syringe, the paste is good as new.
Thanks for all the help guys! Much appreciated
Nah man. They’ll never make paste like that again. I WAS THERE!
It’s a Lenovo IdeaPad Z710 (Model name: 20250).
Should fit I believe
this one is nearly identical
Intel 4xxx:
That’s not OLD.
Or is it? 
Get an SSD though. and blow out the dust inside.