welcome to SUcation!
you can use a mouse or tablet as you like. the first step is modelling. build a good model first. it depends what your objectives are...if you just want some nice pictures, you don't have to worry too much about the internal structure of your model. even a lot of exterior details can be created with textures and bump/normal maps. if your model is for structural purposes, then detailed modelling is everything.
if i'm working on a job that needs some renders, i may use one of the many plugins ...podium, IDX, SU2POV, kerky, etc...to export the model and textures. rendering can be time-consuming, so i may start the render process on another computer. then i can carry on working on the model on the first computer.
SU can run on linux i believe, but not without a bit of modification/tweaking. some of the renderers run on linux...povray, kerkythea for example.
there are lots of tutorials out there, and as rclub says, lots of help on these forums
good luck!