w124 transmission slipping

[dirtymoney]

I own a 1990 300e w124 with 256,000 miles. A couple of months ago I let a mechanic friend change the fluid and filter on my transmission. Shortly thereafter I began to have problems (prior to fluid/filter change there were no problems). At first I began to have erratic shifting, now the car will not go into high gear, just revs freely. Any input would be appreciated. Seems to be a lot of discussion on the modulator (hope its that simple). I dont see any leaks but now fluid is disappearing. No blame to the mechanic as he more than competent for this simple job (tightened to spec in star pattern). I was told to leave that fluid alone and sure enough I see on the forum that this problem happens after fluid changes. Introduced gremlins in tranny when it was opened i guess.