There are loads of differences DBPro is a completyely re-written engine. YES you can use Pro without having to own or know DB1
The best reasons to use pro are: IMHO
Much faster
More stable in XP
Split screen possible
Many new Shadowing and lighting effects
Proper file accessing and editing
DLL support & Online Multiplayer (You CAN do this in DB1 but need to buy Dark Matter expansion)
BSP Support (eventually
)
Basically much more proffessional results are possible
The reasons NOT to use it and stick with DB1 would be ummm
1. Its cheaper and
2. There are less bugs (but DBP is getting patches all the time to fix this
)
I would recommend Pro, its really good
As for model/level editors I recommend Milkshape ($20) Cartography Shop ($40) and PaintShopPro ($70ish) for textures. Others strongly recommend Quark also (FREE
)
Hope this helps