What I believe to be true:
Sandblasting can distort large flat panels but it is OK in fact good for things like gutters and sills
Sand blasting may find areas where the metal is thin or rusted and make these into holes, IMO you would want to find these anyway and fix them before any paint goes on.
Flat panels can be relatively easily stripped with paint stripper and this will save you money when you go to get the rest of you car sandblasted. (if you do)
IMO you want to take all paint you can off(certainly outside) there is often (at least on my car) rust hiding under paint and there is no way you can see it.
My little brother didn't like the idea of using a wire wheel as he said this can heat the metal and cause distortion of the panel I am not sure about this and I have used a wire wheel and had no problems as far as I could see.
I reckon your best bet if you are prepared to do some paint stripping yourself is to strip as much of the flat panels and easily accessable areas as possible and get the rest blasted. This saves you money but gets the best job possible I think. Talk to your chossen panel beater / spray place and see what they say.
Oh and let the panel beater organise for the sandblasting as they will want to get some paint on it as soon as possible to stop it rusting, or at least make sure they can get it sprayed soon after being blasted.
You don't want to leave the metal bare for any length of time, you can temporarily spray it with primer? to stop it from rusting and this will come off with a quick rub with thinners if need be.
well that's my 2 cents