you might want to put a warning in here somewhere about possible unstable rock conditions on the Apron above- there was major rockfall a few years ago from Glacier Point Apron, & also another major incident recently (a month or 2 ago?), that inflicted major damage on some buildings at the base.
The major rockfall was east of the Cow - don't climb anything East of the Cow or West of Monday Morning Slab. Routes in between those two points are " probably " ok, although I'd like to know more about the last rock fall.
We found the above approach beta hard to follow--in fact we went one pitch up a different 4th class gully before we realized it wasn't the right one.
Simple instructions for the approach are: as above, follow the trail from the NE side of the trailhead parking (do not take the trail right off the road, take the one that stays about 25 yards from the road); stay on this trail for about 1/3 of a mile until you get to an old fire ring/ampitheater. You can't miss this. From there, angle up right to the base of the Apron and follow it left until you see easy 4th class start and an obvious splitter crack above.