Welcome aboard!
The fuel problem for the fleetboats is something you need to address with great care if you want to use the gameoption of limited fuel. If you dont care to bother, then just switch on unlimited fuel.
As for the mods, they come in all shapes and sizes. I would suggest you go here for a list of mods:
http://www.subsim.com/radioroom/showthread.php?t=108964
Ask fellow skippers for good mods to suit your taste (sounds, gameplay, visuals etc...)