mercedesi90e

Great sight, first I have been seaching for the sure answer to my 1991 MB i90e transmission problem for a while now...it has alot of miles has been well kept up...but suddenly the automatic transmission went from no sign of slippage or hard shifting to only having drive gear and reverse...the fluid is fine the kick down switch under throttle is clicking up and down when I do it by hand...I have also unpluged it...is this a simple problem fix with out having to drop trans or what...help please...Its a great little car but only books for about 2,500 and I dont want to put 2,400 in labour and a used trans, any clues where else to check problem.
Thanks
mercedesi90e...mcgdia8@aol.com