Umm...I've always checked them by jacking the car up some, grabbing on the shaft (go ahead and lol) and trying to shake the hell out of it, and trying to rotate it both ways...there shouldnt be any play in it. Also do a visual inspection, IE any grease missing, torn boot etc...
Typically when a driveshaft is bad, it wil pop or click very loudly when turning.
Of course its easier to have someone else do them, but its actually pretty easy to do as long as you have a big ass socket (you can rent a set for free from autozone/advance) and something to pop the axles out with. They are around $80-100 each, and sometimes require a core charge (give them your old ones) The ones I got from Advance Auto parts came with a lifetime warranty too...
Easy way to test if the motor mount is shot (besides just looking at it, which requires pulling the passenger tire) is to grab onto the engine while the car is in park, and try to rock the engine forward. If you can pull it forward fairly easily, then it's time for some motor mounts..
