1) I don't see any problems taking film with you. Burmese authorities have nothing against tourists taking holiday shots but you should not take photos of anything military or even police etc.
2) If it's a guided tour they'll show you everything so just take a LOT of film. You might want to take a flash too as it can be very dark inside pagodas and other constructions.
Bagan is a dream destination so make sure to be on top of a pagoda when the sun sets. Mandalay itself is a mess but there are a lot of nice historical places around it. Burma in general is very beautiful, almost untouched. Burmese people in general like to be photographed so no problems there either. Be prepared to the fact that you cannot buy any photo gear inside Burma. No film, no batteries, absolutely nothing.