3d Canvas and other modellers will allow you to make any 3d maps you want in your game since generally you can load modelled maps like anything else into DarkBASIC, and if I'm hearing you right you want to put your own texture on the map (square pics of grass of concrete or whatever that makes your map have realistic looking surfaces). To put your pic/texture into the map you can either use practically any modeller's texturing interface, or you can texture it manually in the code you put into DarkBASIC.
As for which programs you should buy it depends on what you want to do with your developed games. If you really want to avoid programming 3d GameMaker is probably the best choice along with a 3d modeller for custom content
If you want to pursue a career in gaming (either sell your stuff on the internet, or eventually want to go work for Nintendo or Microsoft), I would recommend buying DarkBASIC and a 3d modeller that seems to suit your needs and is relatively cheap and easy to use.
3d GameMaker is a heck of a lotta fun, though, and I play with it in my spare time for some kicks. If you really want a program that is totally based around making 3d maps you can texture then check out Cartography Shop 3.
Your end choice should really be based off your observations and instincts. It usually turns out good, and if not, that' just part of the growth experience.
Posting on this forum is a good idea, people on here may be slow, but they're knowledgeable and help the new guys get rollin' pretty good.
Have Fun,
Juvy
Juvenile Industries
Current Project: The First Room (FPS)
Side Projects: SHIPWRECK, the boss's school project
