So I got MTW with the Viking Invasion expansion pack last night (yay!) and after spending several hours reading the manual and going through the tutorials, I thought I was finally ready to play. I think I have a fairly decent grasp of how battle works, but the campaign screen totally confuses me.
I’m trying to play the Vikings. One general, apparently, is not very loyal. How do I get rid of him? Also, how do I raid? I took a ship over across to another country and clicked all over the damn place to no avail. I am so frustrated at this point at my lack of understanding that I’m about to chunk the damn game away and forget it. But I’m sure it’s just some little piece of information I’m missing.
Help?
Also, any hints and general strategy would be much appreciated.
Oh, don’t throw it out! M:TW is loads of fun. 
There are a couple counterintuitive things, though, ocean transport being one of them.
In order to transport troops across the sea, you need a ship in each ocean territory between your army’s location and its destination. I can’t recall the details of the map from memory, but I think this means one right next to Norway, one in the deep water in the centre, and then one further one adjacent to whichever territory you’re raiding. Once your ships are in place (note: this means they have to have started the turn in that location), you just pick up your army and drop it on the destination. If the enemy has a ship on their coastline, you can’t invade even if you have a ship there, though; you must first sink their ship.
Raiding with Vikings early is fun. Huscarles will slice through most other troops, especially startup units, like a hot knife through butter.
Getting rid of a general can be done in a couple ways. If you have taken a bunch of casualties and have some units of the same type at less than full strength, you can put all his troops into the understrength units, and then disband him. You can also assassinate him, by building an assassin and then dropping the assassin on him. Assuming the assassination is successful, a new general will be picked for that unit. Or you could just leave him be. Unless the disloyal general is one with titles and a large army, he’s very unlikely to actually rebel. Put him under the command of a strong, loyal general and he’ll behave himself nicely.