Yosemite's high country (Tioga Pass, Touloumne Meadows, Glacier Point, etc) will probably be snowed in by mid-October especially if El Nino forecast for this winter actually happens. The valley floor may also have snow by then. The first major storm usually hits around the first 2 weeks of October. I would have a Plan B in case it's snowing when you planned to visit Yosemite.

Since the number of campgrounds and hotels is reduced from the summer, I would guess that reservations are still tight so don't delay. The good point is it won't be very crowded. You may be lucky and have clear, sunny weather!

The driving route is pretty simple from the Bay Area...pretty much a straight shot east on freeways and CA-120. Any online mapping program will give you the route.

Suggest posting on www.tripadvisor.com in the Yosemite forum. A lot of locals and frequent visitors contribute there.