Actually goes now into reverse when I first start up the car in the morning (car is cold).

I read that this is probably the piston related issue that engages the clutches for the reverse gear. I read that the piston was made of plastic instead of metal, and therefore likely has cracked. Is this true?

So the question is, should I just get the reverse problem fixed or do the whole transmission overhaul. The tranny otherwise shifts fine, and I did the servicing always on time. I got 155,000 miles.

__________________
'90 300E
Lowered with Eibach Springs
Mouldings and bumpers painted body color
Clear front corners
94/95 W124 Taillights