If you are new to 3D, youll find the main bulk of knowledge at the start is just learning all the concepts. Polys, materials, light and shadow, keyframes, composition, camera-work, SDS modelling, splines etc. These things are all fairly universal across 3D programs and can more or less be directly transferred from one to the other. Once these are done though, youll start to learn all the ins and outs of a specific app, this is where you should pick your app more carefully as you can potentially invest a lot of time learning all the app specific parts. But, for the first month or two, any app will give you the same basics.
Some apps are more well known for being a bit different from others or following a more established set of principles. Youll find that c4d, modo and maya are all relatively similar in their general approach to things, whilst some apps such as houdini, zbrush and to an extent lightwave; all diverge a bit in how they handle things.
I have to ask though, who is this altruistic friend giving away thousands of dollars worth of 3D software?..