Hi, firstly, 3D has made my after fx experience much more flexible. Even if you dont want to learn character animating etc, 3D is still very usefull for many effects. You just have to look at the opening to most TV programmes to its its subtle use.
As for learning, I found that for the very basic introductory stuff, just working through the softwares own 'help' files is good. I use 3Ds MAX and the help file has pleantly of work-through examples which taught me all the basic stuff.
Try playing with materials and shaders if modelling gets too much, thats where all the fun is had -well, in my opinion! I made many a textured dinosour egg.
You can check my first ever finished model at http://www.myspace.com/sensillogic
Its not perfect, but I was chuffed with it:)