I recently built my own PC for the first time from the ground up, and found excellent information of all types on the Tom's Hardware site: http://www.tomshardware.com/us/.  It actually turned out to be very easy, and I got a nice high-powered PC for under $1k, buying everything I needed from NewEgg. Between the info I found on the web, and the info provided in the boxes with the motherboard, processor, etc, it took me maybe 3-4 hours over two evenings to get it up and running. I think it took more time getting the old HD from my previous computer working, and updating XP for all the new drivers than it did actually putting it together.

 Tom's Hardware has a lot of info on upgrading CPUs -- considering your PC is a year old, it should be possible to upgrade it fairly simply.  It may be as simple as pulling off the old CPU cooler, removing  the old CPU, dropping in the new on and putting on the new cooler. It's best if you can find out first what kind of motherboard is in your PC -- a goggle search will turn up a zillion free utilities.  I use CPU-Z, which gives a lot of info about your system: http://www.cpuid.com/cpuz.php