That's the ticket, Mate!
2 things: make sure that you're back in port after a mission before you use it with an existing career.
If you're using any mods which alter the campaign files (like Real World, Improved convoys) there might be a conflict, but if you use The mod enabler utility to install it, it should warn you if there are any problems.
I have a stack of mods on my game (mostly graphics & sound improvements) and I haven't had any problems.
Good Hunting!
Hawkers