Had exactly the same issue after I had the serpentine belt changed at Valvolene. Wouldn't shift, no speedo. Took it to a AAMCO and they did a diagnositic for a few bucks and traced it to a loose wire around the speed sensor, probably pulled lose whilst the serpentine belt was changed, and my guess was that yours was similarly disturbed during the oil change.
Hope it similarly didn't cost you an arm and a leg in the end.
Monday, December 1st, 2008 AT 9:28 PM