Railworks America

I don't really have many 3d modelling skills in applications like Blender. I've played with it a bit, but have not had the time to indulge.

However, I do know Photoshop (extended) quite well.
Is it possible to take an existing base 3d model and rework it inside photoshop, or am I forced to go on a steep learning curve and get into Blender or another 3d app?

In photoshop you cannot edit 3d models, but you can either create you own models, or repaint using their respective programs

Repainting
viewtopic.php?f=9&t=1202

Modeling
viewtopic.php?f=9&t=4864

You need a 3D modeling program to model but you can use Photoshop to create repaints which are invaluable to out community.

The tutorials for making a locomotive using 3DC are now on my blog:
http://thegradecrossing.blogspot.com/20 ... tives.html

I would still suggest reading the other topics (the two provided by Arctic Cat ZRT) as they have plenty of handy tips.