ORIGINAL: Libertarian
As far as the air scoop is concerned I'd get it (and any reserve parts you might like to have on hand) from Redrockethobbies.com
A guy named Matt seems to run the place and will give you $5 off if you order more than $50 (I think).
From the reviews I've read the Mustangs won't take off from the ground unless you add a working rudder and 4th channel and of course all the new radio gear replacing the old stuff.[&o]
Ditto what Lib said.
You need to remember my Stang has a hot brushless set up in it, so it can handle the weight of the retracts. I guess you could install a set of non retractible gear, similar to the E-flite P47.
Still have to go with hand launch, but landings may be a little easier. If you do go this route, be sure center point of the wheel is ahead of the CG, otherwise she'll tip on her nose.
bkrfrmhell,
Good set of tips. Might add the check the control tubes for loosness too.