I own an AVN2494, but am about to give it to my dad and plan to upgrade to the AVN5435.

I had my unit installed over a year ago by my friend who sold it to me. What I was wondering was, is it easy/cost efficient to get some upgrades done at a place like Tweeters or a similar car audio place? Specifically, I would want to add a CD changer since the OEM lexus one is not compatible with the eclipse units, and also a rear-view camera. I also still have not bought a new amp & sub, since the factory sub is not compatible with the eclipse unit - but I know this is pretty easily done anywhere.

I remember the Eclipse install being pretty complicated and taking a while, and am basically looking for the quickest and most painless way of getting it taken care of. Any advice?