Best to do it yourself. It only takes basic tools. A lot of time shops just power flush it which does not change the filter. How many miles are on your car?
I've worked at a lube shop for 2 years and we do either a tranny flush for 79 bucks or we drop the pan replace the gasket and filter for 49 bucks plus the tranny kit. I'm assuming its a auto?
When you do the pan it only gets about 40% of the old fluid out. Because all you are getting is the fluid in the pan and filter whats in the lines stays in there. A flush gets it all. What I suggest is that if its really dirty do the flush and the pan. The flush is pressurized so it will clean some of your filter out. What we tell people is do is if it is the first time you've changed your tranny fluid then to do the flush, next time do the pan.