How easy is it to upgrade a PSU (for someone who is not well-versed in monkeying around inside a PC cabinet)? My PC has a miniscule 250W PSU, which takes pretty much any graphics card improvement above the GeForce 7100 currently installed off the table. But I'm terrified of destroying the computer if I attempt to replace the PSU with something stronger.
In some ways it's the easiest upgrade, in some ways the worst.
Everything is plugged into your psu. So you have to unplug everything, and then plug everything in again with the new one. This is worse than it sounds, because you're working in a cramped space and untangling an octopus of wires, keeping different plugs/voltages sorted, etc.
In the other sense, it's easy. A 4 pin molex only takes a 4 pin molex plug, it's pretty straightforward. Just don't forget to plug something important in.