This would probably be more relevant in the game engine section of the forum, but…
Most people on the forum officially license their content as Creative Commons or some other liberal license. If posted content (.blend files, etc.) is not specifically licensed then you can contact the original creator and establish their usage rights.
As for help on how to model your mind’s creations… There’s a whole world of tutorials out there. My advice would be that if it’s free then follow it. If you have to pay then consider carefully the source. Once you’ve followed a load (months worth) of free tutorials then you should have a good idea of how to progress and have a good idea of which paid tutorials will be of most use to you.
Best of luck and most of all, have fun.
One of the best things about Blender is no install is necessary. Unzip it to a memory stick or usb drive and then just open the program from there. Try doing that with the huge file sizes of commercial software :spin:. You can keep your current version of Blender and all your files on your usb drive and take them with you.