Reroofing

I have a tile roof that is about 18yrs old, it started to leak at some of the valleys and the two sky lights, I was able to take the tiles off and repair but with recent hard rains the roof has developed additional leaks, no one in my area is interested in removal of tiles, repairing/new felt and reinstallation of tiles, I have been told that the felt paper on it is 90#, since it looks like I will need to re-roof with shingles what weight paper is best to use???, what questions should I ask contractors??? I live in Central Flordia, thanks for any help