Actually, I just read your post a little closer. If I were you I would stay at Lee Vining for part of your stay and see the East side of Yosemite and the Kennedy Meadows area. Then go ahead and take the motorhome over 120 and stay at Yosemite Pines RV park in Groveland or there is a park closer to the park on 120 too. Then go into the valley in the toad from there. Then when you're done you can take 120 on down to I-5 and work your way up to Crescent City. Per the Caltrans website and the Yosemite website you can drive up to a 45 footer over Tioga Pass. I've done it several time in my 35 footer and it's slow going, but very doable. Just use the turnouts and take your time.