Newbie vs. PSU

I know virtually nothing about the considerations that go into the investment of a PSU. Fact is, my understanding is limited to this: My PSU is beginning to die, and I need to purchase one that is a suitable make/model for my system. Unfortunately, I'm also aware of the plethora of options out there, and that's causing me some hesitation. (Let me admit: I'm only assuming my PSU is the cause. I recently replaced my CMOS battery, thinking that it was the cause early on, which is wasn't; I replaced it with a new one, anyway.)

My setup: An unmodified Dell E510. "Unmodified," because I figure that's worth mentioning when it regards the transplanting of vital components.

I'm not sure as to the specifications of my PSU is; I don't know where to look, what to check, or whether or not I should poke/prod my way into finding this out. Thing is, I'm notoriously clumsy, and fear I am break what I seek to preserve, and I'm slow to learn the rudiments to PC maintenance.

So, given my PC (make/model), is then a generally accepted standard of PSU that I can consider to be my first and final go-to solution? Thanks in advance; and, thanks again, for putting up with my lack of PC know-how.

Wow, are you kidding me? Are things just that simple/easy?

Christ. I'm floored.

How to replace the PSU is down at the bottom of the page:

http://support.dell.com/support/ed [...] #wp1370145

Things are that simple - until/unless things go wrong.