Hi, Cal! I am slap bang in the middle of finalising an exhibition so I can share with you some of my experiences. Unfortunately, I think a lot of my observations on your questions will be "it all depends"! Nonetheless ...
a) exhibition size prints? Mine are printed at A3 and then mounted and framed - so if you add about 3 inches all round to the A3 that will give you the rough size. That is big enough for the gallery I am exhibiting in. The size of your prints could depend on the space available to you plus the surroundings of the space plus the number of prints plus, plus ..... Also in terms of size, I am hoping to tour my exhibition so a reasonably average size suits my purposes. If you are thinking more of a one-off, that could influence size.
b) cropping - yes but up only up to a point. Most of the images I have chosen are uncropped though I do have one or two which have been slightly cropped. The images come from 3 different cameras - I have a couple from a 5mp compact (Olympus 5050) which, believe it or not, are absolutely fine at A3. The others are from 8mp cameras (one SLR, one compact). I don't believe you need lots of megapixels and the latest DSLR to take good shots
c) I have arranged for the printing for my exhibition. To be honest, I wouldn't want a gallery doing it for me (unless you are talking about them paying for it!! I think that would be pretty unlikely, though).
I have 50 framed images which will be on display. They are all underwater - 40 of them are from Scottish waters and 10 are from overseas. The gallery is a museum and art gallery which has a permanent collection and then has temporary exhibitions throughout the year in one of its spaces. These temporary exhibitions are wide and varied so underwater for them is something different which they are quite happy with. Not all galleries would consider it though. I am aiming at a very generalist audience.
There are lots of things to think about in preparing an exhibtion and lots of tasks (designing posters, flyers, etc). It also costs money so it is a good idea to look for sponsorship or grants.
Below is a thumbnail of a printed flyer for my exhibition which opens next month and feel free to PM me with more specific questions.
