My 1995 E320 wagon transmission has started to go. Works fine in all gears except reverse. It takes 2-3 seconds to engage. It struggles/slips when backing up hill and it pushes against the brakes if backing down hill. I had the transmission serviced 2 months ago. My mechanic looked at it again last week and said the problem was internal.

Any estimates on how long I can get out of it if I baby her (ie. let it take time engaging, don't park pointing downhill, try to find parking where I can pull through etc..)?