Hey guys so I was thinking about making a whole new questline and world for new vegas, I have never attempted to mod Fallout however I know how to create textures meshes etc etc, however I am not experienced with the GECK but I can get the hang of it and was wandering if anyone could help me get the hang of it, cheers.

I'd really recommend checking out this guys tutorials:

https://www.youtube.com/channel/UC8xg-EQk4U5AmkvBJfHGYDg

There the best on questing in GECK available

This advice will be boring, but you're better off learning how to do small/simple mods in the GECK before undertaking something of the scale you're talking about. You do the wrong thing creating/editing quests and you break your game.