In reply to cballard: doing a big wall , in this case el capitan, is a really cool experience, hardly comparable to climbs in the alps, so I would definitely go for it.
If you can lead E2, have enough experience placing pro ( what you have), the only other thing you need is figure out the techniques for hauling, jugging ... and build up enough motivation to keep going up after a ( usually ) hard first day. Higher up, it's getting easier as systems are dialed, bags get lighter and the top out gets closer:
your freeclimbing grade is pretty irrevelant for aidclimbing only routes, experience in managing complex belay situations etc is important. for zodiac, climbing shoes are not a must , so ...
my advice:
get a book on big wall techniques, practice some aidclimbing to move efficently, and for about half the money you pay for a guide you can buy the extra gear you need.pick a trade route to start with , best having easy hauling, Zodiac or tangerine trip are good routes to start with: short , steep and not too difficult/tricky.
Lurking fear is easier but the hauling is a pain and it's not the typical bigwall ( more slabby)
the nose, triple direct and salathe are great routes, but more free climbing, longer and thus logistically a bit harder
so yes, do it!