Oh come on...the freehub would only cost a guy that works in a shop $50-$75 (retail on that part is $125 from Bontrager). and I am sure one of the shop guys would install it for free if the OP couldn't do that himself.

What kind of rider are you? Sprinter, Climber, going for wins in solo breaks? If you do a lot of RRs and try to go solo then you want the aero...if you finish in the pack most of the time and are sprinting for wins or if you are a climber then go for the XXX Lite (I haven't checked the specs but I assume they are in fact lighter than the 5.0?).