Just some thoughts on the top 3 most intrusive pieces of computer hardware to upgrade or replace:

1. Case: You have to take everything out, completely disassembling the machine.
2. Motherboard: Disconnect every data cable, pull out every card, and sometimes even move the spacers that connect it to the case.
3. Power Supply: Disconnect power from every drive and from the motherboard, and possibly move stuff out of the way so you can get at the power supply.

Then, of course, you need to do the whole thing in reverse.

One reason I haven’t upgraded my processor lately (a simple procedure by itself) is that whenever I do, it seems to need a new socket, which means getting a new motherboard. Which also needs new memory…