Is replacing the head unit in the vehicle a DIY job? How about the speakers in the dash, doors and rear?

My deck broke a while back and no longer plays CDs, only the radio. I would also like to have interoperability with my ipod/iphone. This indicates to me I either need one of those integration kits or I need to replace the deck entirely with a new one that has that function built in.

I would prefer the stock deck, but don't think it will be worth the cost to repair it if that is even an option. I'm looking for any suggestions/guidance in regards to a good replacement for it.

I'm also looking for guidance regarding replacing the speakers, as I'm fairly sure one or more are blown/broken.

 

http://www.car-part.com/ for the head unit, because the 6th gens have a unique head unit.
http://www.crutchfield.com/ for speakers. They may not be the cheapest; but they're close to the cheapest, only offer good product, are very knowledgeable, and have unparalleled customer service.