i wish i could choose between cars and planes like that. I thought when i got into planes i wouldn't want to run the cars anymore, thing is though, if the weather isn't favourable for flying more often than not it's perfectly good for some land based fun. All this was of course a number of years ago now, and i will admit my plane collection is expanding faster than my car collection [:-]
Anyway, pretty much as above, Your knowledge will help with radio installation, and to a small extent the tuning too as with planes you go WOT tweak the needle for max RPM then back it off a bit, sooo much easier than with cars. Your experience with cars will give you a slight advantage when flying towards you too but it wont help much for the general flying
The sims are pretty fun, but once you at the field with a couple of hundred quids worth of parts strapped to few thin bits of balsa and ply it's a whole other story

unless of course you one of these new fliers who seem to know no fear [X(] hehe
Bottom line, find a club, go for a visit and take it from there [8D]