I usually fish the Pit alone, and have never had any problems (knock on wood) with injuries. Be sure to have a staff, such as a ski pole, studded boots and just take your time. Try and keep three points of contact as you wade up, and if you feel yourself slip just go with it, rather than jumping around trying to find another rock - this is how you go swimming.
The Pit in March can be hit or miss, depending on the recent weather. It seems like we're in a dry spell right now with some warm weather on the way. The water will still be cold though, and the trout may not be where you think they should be. If you're not getting hit in the usual pockets and runs, try some of the slower tail-out and deeper pools.
Access three has some great water, and this time of year fishing the more popular spots should be just as productive as hiking a ways into the canyon. Like Pound said, the first stretch below Britton can be good - just hike down river-left as far as you can and fish back. The flies that Pound mentioned will work but be sure to have lots of weight and fish each pocket/run thoroughly. This time of year it may take a few more casts in front of those trout to get em' to bite. Good luck and post a report, if you make it back
-Notch