do you know if it's a slot style (as in, a long processor that looks somewhat like an old style video game cartridge) or a socket style processor (as in the fan and heatsink account for most of what you see rising up from the motherboard). if it's slot style I think you might have some problems. I've been out of the loop for a couple of years now, but I think all the newer processors are socket style.
at any rate, correct me if I'm wrong, but I believe the duron would use either a 'Slot A' or a 'Socket A' motherboard, same as the Athlon. if this is the case, you would be able to upgrade to an Athlon processor, which is far superior to Duron.
but I could easily be wrong about all of this, so don't take my word until someone else confirms it.
now to the issue of instalation. if I was in the position to be held liable if you went and fried your board/processor, burned down you house in a ridiculous display of noobism, or put your eye out on the corner of the mainbaord, I would say that you should probably have a pro do it. likewise, if I was in the position to make money on the instalation, again I would tell you to have a pro do it, and give you my card. I am, however, in neither of these positions. in all honesty, it's pretty easy to install hardware, be it mainboard processor or ram. if you can assemble a snap-together model, if you can if you can transform the easiest of the Transformer toys (think Bumblebee), if you can wipe your butt without the aid of a mirror, the the only think that will acount for failure in putting together the modular components of a computer is intimidation at the prospect of it. that and an inability to ask questions when you aren't sure about something.
in a sentence I can sum up 90 percent of what you need to know: if it doesn't fit, then it probably doesn't go there.
beyond that, and anti-static strap is a good idea (this is really more about insuring the expensive components you bought. in all honesty, you could probably build a pc in a balloon testing lab without any trouble), make sure the components your buy are compatable, the red stripe on ide cable stays on the outer edge, and make sure everything is firmly seated.
but if yours is a major name brand computer, then all bets are off, cause they tend to be proprietary as hell.