100,000 on a 124 trans is a lot. I know that sounds crazy given what other makes will go, but the Mercedes transmissions seem to be pretty short lived. My 92 300TE only had 138,000 and the trans was shot. A rebuilt trans from Sun Valley was $1750 plus $250 shipping. I have been extremely pleased with the trans and I'm approaching 3000 miles since I swapped it out with absolutely NO issues. I will be performing regular fluid and filter changes, in hopes of keeping this one alive a little longer than the original, but figure the engine will give up before another 100,000.

My suggestion, being it is a friend, would be to do the kickdown switch change, with the understanding that if it does not fix the issue, the price of the car will have to be negotiated. If it fixes it, you get a nice car. If not, you need to plan on sinking about $2500 into a trans swap, cooler lines, new flex discs and trans mount as soon as you get the car. Ask me how I know.