First off....Welcome! :o)

Now, to answer your questions:

1. No, props for M3 are not compatible to M4. However, prop hair especially can usually be tweaked to fit another character...some of us do it all the time. It takes a little moving, scaling and maybe a magnet or two, but it's not that difficult.

2. You can make any texture you want for a model by painting your own onto a texture template made for that model. You can't use a texture that someone else made either for a base for your texture or for parts of your texture if you plan to sell the texture itself. If you plan only to use it for yourself, that's different. If you are making images for a book that should be alright. Of course you can always start from scratch. There are a lot of us here (myself included) that do a lot of texturing if you should have questions.

I'm sure there will be someone else come along who will go into a bit more detail; there are other comic book makers/graphic novelists here :o)

Hope that helped some.

Have a great day!

Laurie