I had a similar problem with the overhead light, turned out that the metal connectors were loose, a quick fix. It could be something similar for you though I haven't dug that deeply into my cars interior (stopped at the CD player, never got as high as the ac controls.)

As for replacing, to save money "I" would do it myself. You first need to remove the paneling around the shifter (can be popped out with gentle flathead leverage) and you then want to remove the 4 screws (right under the ashtray/ lighter) the HARD part is getting the CD player out. If you have the keys to do so, lucky you, if not, Ive found that jigsaw blades can work... somewhat...

Everything else should pop out after that...