Parking is still available and the Market Street exit to 76 is fine. Vine Street is a little more dicy as the exit to the art museum is closed. If you take 15th street you will get here but it will be a little slow.
The half marathon is finishing now. That should free up more parking! Right now plenty at the lot on northwest side of 22nd and Market.
I even got my usual spot behind the Mutter Museum (21st below Market).