| Right off the bat, in my experience, mouth tumors are nasty. They're usually bad, but it depends on what type of cancer it is and if they can get all of it, and sometimes radiation or chemo is recommended.
If you haven't already, I would see a veterinary oncologist about what your best options are.
I did see a dog a long time ago that had a procedure where they took quite a bit, and though he looked funny, he seemed to do ok.
Also, as far as adjusting goes, dogs seem to adjust to just about anything. It is common for little dogs to have bad teeth, and it is not uncommon for them to loose their lower canine teeth, which causes less calcium to get down to the other teeth and jaw. I have seen alot of little dogs that have a lower jaw that basically isn't there anymore because of this, and their tongue flops around more, and it is a little harder for them to eat, but they do it and go on about their lives just fine.
Please let us know what happens. | 
