If you use reverse constantly, it will wear a little quicker than normal.
The thing I would do is remove the trans and pull the front pump. If the reverse clutches are worn, I would replace just them and not rebuild the whole tranny.
If this is the problem (and it is most of the time), It would cost about $1,200-$1,300 to fix at my shop.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS