Tums is simply calcium carbonate, and is generally used for symptoms of acid reflux like heartburn. It probably wont help with gas and bloating or diarrhea. It certainly wont hurt, and the usual dose is 2-4 tablets depending on the strength.
You should see your doctor to discuss medications you might need to bring down inflammation in your gut. Tums isnt going to cut it. You could try something simple like probiotics at first, which can sometimes help with diarrhea, but if your crohns was severe enough that you had a resection, you will probably need some form of anti inflammatory medicine.
As far as your symptoms go, you could try taking Gas-X (simethicone), it wont help the underlying problem, but might make you feel a little better in the meantime. Also you might be eating foods such as vegetables or things high in fiber that are contributing to your bloating.