Picking and ordering parts is relatively easy once you know your budget and what you're looking for (gaming/rendering and processing/how long you expect the machine to last)
Building it takes a bit of work, you can always pay the store that you ordered from to put it together for you(eg. NCIX $50 to put your entire system together)
I'd suggest
1. shop
www.ncix.com
2. pricematch with shopbot.ca
3. ???
4. PROFIT