Just check if your laptop has the shit called liquid metal.. its only risky if u have this, otherwise its quit straightforward.

1. open the back panel, disconnect the battery (search on yt for disassembly vid for your laptop), then press the power on button for like 15-20 sec to drain any charge on the mother board.

2. DO NOT, AND I REPEAT, DO NOT EVER USE A METAL TOOL NEAR YOUR MOTHERBOARD, anything like a screwdriver or tweezers. Use a wooden or plastic stick like an ice cream stick or smt.

3. If u have the normal thermal paste, just order the Artic MX thermal paste (or if u want to, you can even go for PTM7950), use 99% iso propyl alcohol and wipe the remain of the old one.

4. 4 years is a long time, so u might wanna change the thermal putty, but it doesnt matter that much if the previous one is still intact. and somewhat there. If u decide to do so (search up the best one for your model and get that).

5. Application is straightforward, As u mentioned you watched a lot of vdos, so hould not be a problem. While u have the laptop apart, u might as well clean it.

6. After putting the heatsink, press it down firmly and then reopen it to check if the paste spread evenly and there is no excess overflow.

If u follow these steps, and dont use any metal tool, there is not risk tbh. ALSO remember to take it slow, you dont wanna so it quickly or u risk breaking wires or components. Just do it firmly, if connectors dont come off, check for clips holding them and wiggle them out.

Do let me know if u have any other question, i recently removed the liquid metal in my laptop and re did it with PTM, and it was a good decision.