Exit 38? That is out towards Pittsburgh.
There is only 1 East/West accesible Service Plaza at Sideling Hill, Milepost 172.3 in the middle of the state.
But it is not an exit, so you would have to both continue along. Pick an equidistant exit and both get off, then you can get back on to go back home.Edited: 5:55 pm, March 21, 2012
I'm guessing OP was using the old turnpike exit numbers... I still tend to remember some of them that way too. I wouldn't meet someone at a service plaza. LIke Mike said, find a good place to get off and meet.