First off welcome and enjoy the ride (as well as an empty wallet).
Second go here:
and read all the stickied FAQ's
Third, read them again
Forth, revise you profile with your location. The local players in your area can help you a lot more easily with what options and requirements are available in your area.
As for your questions, yes you can have TM guns, any of them, but you'll have to get Age Verified to do that (info for AV is in the FAQ). You can sometimes get them from retailers here on ASC as well as in the classified section once you're AV'd. What you can get really depends on what's available in country.
M10, ok gun. Small, short range can't upgrade much. Basically a glorified pistol.
M1A1, great gun, super strong gearbox. Fairly rare. Mags not too easy to find in country, but easy to order from overseas (ok to import these mags). The connection from the barrel assembly to the reciever is a bit on the weak side, so don't fall on it. There's not much for accessories for it either.