New Sound '05 Aveo Hatchback

Have a few questions as I've never installed any sound equipment. First is how difficult is it to install new stereo deck? Little weary of miss wiring something there. Considering just letting bestbuy handle the desk installtion but I don't want to waste that kind of money. :mad: The speakers I don't think I'll have any issue with.

The next question is what would be recommended for rear speakers? 4" by 6" right? I'm thinking of going with these for my front doors.
Polk Audio DXi400 4" 2-way speakers at Crutchfield.com

And, lastly are there any single decks anyone would recommend. I don't plan on adding a sub. I'm considering this one Pioneer DEH-3400UB CD receiver at Crutchfield.com currently if I do it myself.

Oh, my budget is $200 to $300. I listen to mostly Electronic Dance Music (house,hcc, trance, ect.). So, lots of Highs and Lows. Can't afford to use up my precious space for a sub though. Thanks for any help/suggestions in advanced.