A hacksaw is a good way to cut large gauge wire, as well as a rotary tool with a metal cutting disk.

For attaching the terminal lug, I would suggest soldering it over a crimp.

Here is a nice YT showing how to do it. http://www.youtube.com/watch?v=SXDkNMDDrBs

If you need to do this in the boat. I use vise-grips to hold the terminal an place it on a block of wood. Instead of a torch, I use a heatgun.