If you already know how to sculpt in real life then Mudbox or ZBrush will be your best programs to use.
You can take it a couple of ways:
1) learn to create a base low resolution mesh in maya and then import that into Mudbox or ZBrush and take it to a high level
2) sculpt your model at a high resolution straight away in Mudbox/ZBrush and then re'topologise' a simplified mesh over the top. An example of software that allows you to do that (though I think its still in closed beta) is somthing like topogun. I've heard mention of Silo and another program also having this capability built in too.

Mudbox is designed to be real easy to pick up and sculpt so it might be a good idea to grab a demo from their site and see how it goes.
ZBrush has a lot more to it and can be seen as harder to get into based on the interface, although there is now an easy to use mode. ZBrush also has a retopology tool although from reading about it, it sounds like it can be difficult to get used to initially.

The best advise I'd say is to see if you can get demo's of each and give them a little play. Then whichever you find better go with.

Simon

p.s, I frequent the mudbox forums (only to read) and there are a lot of traditional sculptors on there who are moving into the digital world. I'm sure the ZBrush forums will have the same type of people too. If you get the chance have a loo at them both and see if there are people already on there that have posted advise or can answer any more of the traditional arts style questions.

Good luck