How much would it cost to redo a 2000 BMW 323I sports transmission?

I was looking to buy a used car and am looking at the lower price range. I found a BMW 323I sport for 3300 but it doesnt have reverse so I would probable have to replace the transmission right? If its not to expensive I might do it.|||BMW parts are out of sight. you can check on line for a replacement/rebuilt transmission. Or for an average cost in your zip code check repairpal.com Or take to a specialty transmission shop and get an estimate to fix your old one, as it could be something simple.