The word for "dry cleaning" is "pressing" in French. You will find them absolutely everywhere. Some but not all do express service.

If it means at hotel, it depends on the type of the hotel. At business hotels in big cities, I have never had problem finding one. Even if I did not care to have them dry cleaned, sometimes, they went ahead and dry cleaned cotton pants. If may be more troublesome if you want it done at small hotels on weekends.

"Pressings" in Paris are like Dunkin Donuts in Boston: you wonder how they make a living because there are so many.

Wool trousers aren't very hard.

Are the prices pretty much the same at the various places? Generally to have pants drycleaned what is the usual timeframe? Thanks

no, it's like any city. Prices vary depending on the location of the shop, same as for lots of businesses. Shops in the most expensive arrondisments will charge more than in the outer burbs.

A pair of pants would probably be between 4-7 euro depending on the shop. I'd guess a couple days would be a normal timeframe. Here's one Paris chain that has pretty good rates but they aren't in the most expensive areas
http://www.harmony-pressing.com/