Get estimates if you're having it done at a garage. The Chrysler dealership where we bought the vehicle was charging literally hundreds over the Pontiac dealership that did the work (I think we paid less than $100, but cannot really remember now).
You can do it yourself (I just spoke to my son). He says go into Auto Zone (or like store) and buy a can of R134A if the vehicle is newer than 1990, or R12 before '89. He said this will be under $4 a can. He then said you'd need to buy a $15 tool (depending on which product you buy). From here, talk to the guy at the store because I don't know the specifics

(I didn't ask my son the process, but he said anyone could do it). In this case, that would probably be, anyone but me!!!!