Hi everyone, I know this has been done a gazillion times, but having searched for a day can't quite find the answer to my question.

Car is a '98 R Leggy type s, auto. Only just got the car, and have put it through an MOT which it passed first time. Car hadn't really gone anywhere in the previous couple of years according to the previous owner, but had been regularly started and moved on and off drive. When I picked the car up from M.O.T. centre and drove home, the gearbox seemed to slipping especially in the first couple of gears from 2-3k revs. I've checked the A/T oil and the level seems fine (covers the plastic gauge, tested in neutral with engine running, which I assume is correct?) but in all the mountains of paperwork I received with the car, the last time I can see it was changed appears to be 2007. Although it was changed every other year before that by the same owner so it's probably been done since, although I can't be 100%

Does this sound like it could be an oil problem, or something else as well? Also, will it be ok to drive, or will I be doing more damage? I'll need to change the oil regardless, so what do people recommend, any links as well would be extremely helpful. TIA