I am scared to think the prices you could be quoted to inspect a BCD it should be free if you are getting your regs serviced and a refresher from the dive shop but thats how I would run my shop ymmv.
To inspect a BCD Look over the outside for cuts broken parts and any dry-rot then I would blow it up with the inflator make sure all the dumps open and close properly and dunk the power inflator to check that the inflator doesnt leak. After that I would stand it in the corner fully inflated overnight if it looses air then something is leaking and would need to be dunked to see where it was leaking.
Other than that a good test dive with your gear should be included in the refresher course to fully test you and your gear (pool or very benign conditions preferably).
As well as standing it overnight, using a bath full of water would also suffice for checking it so long as you can immerse every part at some time. Also using a soapy solution sprayed on it can be a good indication as any air will be caught in bubbles.