Bec you've mentioned transmission that makes me think you must be talking about CV joints or drive axles and they vary in prices but some you can buy as a rebuilt and with a full lifetime warranty for about 80 to 120 bucks.Just keep in mind that there is a core exchange value or deposit that is refunded once you bring back the old drive axle and that brand new drive axles cost on the avg more and have the same exact warranty a lot of the times as the rebuilt's.
Some shops will charge about 90 mins for that job and bec others have better tools etc they might charge 45-60 mins labor fees.The over all cost if you bought the drive axle yourself and shopped around for parts and labour costs would be about 160- 230 bucks.
Hope that helps and best of luck.By the way it's best to change both sides drive axles if possible bec more then likely the other one is slightly worn or will end up going faulty in the near future.There are obvious signs that you can look for such as the inner or outer boot on the drive axle is swelled or loose or damaged or worn or the boot's clamp is loose etc.
