99 Blazer Air Conditioner

I have a 99 BLazer with 156K miles. The AC went out a few years ago, we just never used it after that. Recently a new (few months old) serpantine belt broke and it seems that it was caused by AC unit locking up. I'm not interested in putting in a ton of money into the car, but everthing else works fine. I thought the AC was not working because of a leak - but now I think otherwise. Any ideas? Is the AC unit difficult and expensive to replace? Does it have to be done at a shop?

Thanks.

Welcome to AF
In the USA you can work on a R-134a system your self.
North of USA in Canada ut Alaska I think you have to be certified to work on it.
You replace parts not the hole AC unit.
Cost will depend on what is bad or what all you need on it.
If compressor pulley/clutch locked you will need another clutch and hub pulley to start with.
And before you can charge and run and check out you ac.
One of the most expensive things is a evaporator core leak.
Labor and parts both
Might be as cheap and or better to replace the compressor.
Consider and price a new over rebuilt.
Or on the other hand you can get a non ac belt kit and just remove the old compressed.