<< If you where in my shoes here, what would you do? >>
Remove the ceiling completely.
<< I have no experience with sheetrock >>
Easy to learn. Local library, this NG archives, lots of books at the box
stores. Look at the tools the pros use at the borg or Amazon.com or Google.
Use a mold resistant sheetrock (only costs a maybe a dollar more than
ordinary). Setting type mud and fiberglass tape will resist mold better than
conventional mud and paper tape because mold can feed on PVA in the usual mud
and breed in untreated paper. Use a low platform to work on, made from some
storage crates and planks. Get a shop vac and a Magna sander rig for dust
control. Effective low angle lighting will highlight flaws so you can perfect
<< I was going to put a vent fan in >>
Consider hiring this out after you buy the fan you like. Best done just after
the ceiling is removed.
Now go ahead and do it, and good luck.