Connections are poor between the Fresno Airport (FAT) and Yosemite. No, I mean they absolutely suck--sorry. Try to get to Merced Airport (MCE). Unfortunately, Merced is served by only one obscure airline, Great Lakes Airlines. Amtrak also stops in Merced. See
http://www.nps.gov/yose/planyourvisit/directions.htm
http://www.yosemite.com/tripplan/transportation.html
Merced is important because that's where the daily bus stops between Merced and Yosemite Valley. Take that to get to Yosemite Valley See
http://www.yarts.com/
Once you're in Yosemite Valley, you have it made. There's a free skiers shuttle that runs between all the hotels in the Valley and Badger Pass Ski Area. You don't need to be a hotel guess and you don't need to buy a ski ticket--it's truly free. Ask in the hotel lobby when you get there.
There's also a free shuttle bus that runs in the valley daily.
From Badger Pass Ski Area, head out on the Glacier Point Road. Most snow campers snowshoe, but a few cross-country ski. By March the snow should be consolidated enough that you'll have no problem sinking in with snowshoes (and sometimes even without). March days are relatively mild (down to the 20s or so F), but snow storms can still occur.
At Badger Pass, check in at the Rangers cabin, a "A" frame cabin at the north end of Badger Pass Ski Area. Get a map there and a Wilderness Permit (no problem getting one that time of year). See
www.nps.gov/yose/wilderness/
The summer trails are covered with snow, but ski trails are visible. Don't walk in the ski tracks--walk to the side if you're not skiing. Here's a ski map (click on Badger Pass)
http://www.nps.gov/yose/planyourvisit/brochures.htm
I gotta go. Maybe someone else will chime in with more tips. Or ask more questions.