Wait... Are you designing a typeface or are you replicating one that already exsits?... and are you trying to design the type with the 3D software or are you importing the curves into the 3D modeling software? Also are you hoping on animating the type with motion effects?

Rhinoceros 4.0 is pretty easy to get a handle on. (Don't download the beta version for Mac, it sucks.)

3D is a large and multifaceted field (please ignore bad pun). When it comes
to choosing an ideal modelling application, it vastly depends what your goal is.

The way I understand it, Maya is one of the most important 3D modelling programs for animation, whereas Rhino is geared more towards construction.
So something like Rhino may be worth looking into if you're looking to recreate 3-dimensional lettershapes through rapid prototyping or some such, whereas Maya and the like would be better for hi-fi screen presentations.

In your case – do I understand correctly that your end result should be workable as a font?

If yes, you want to be able to output vectors. Beware because some/many modelling apps are mainly geared towards outputting raster images (though I'm not up to date on output options in all those progs). That should narrow down the field quite a bit. & then of course you'd have to decide if you want something that's as simple as possible to do your job, or a full-blown modelling program that you'll use for a number of things. (In which case, do beware the learning curve.)

Swift 3D might be worth looking into. It's made for compatibility with Flash, but can output all sorts of vector data (like SWF, EPS, AI, SVG) as well as raster images. It's also not too complex, but of course also somewhat limited compared to the "big" apps.

Good luck!