Spoke to Christine, my vet, today. To quote her "I think it is worth a shot, will be big endeavour but the only way forward".
So we scheduled surgery for Easter Tuesday - 22nd April. She will be dropped off in the morning and will have the surgery done that day (or the following day if they have emergencies come in after the Easter long weekend). As stated previously, she will have a whopping great big hole cut out of the side of her face for access to the tumour. Apparently the tumour is more pushing out rather than up and in (which is a very good thing!) however one or two teeth may need to come out. Christine is not worried about the infraorbital nerve anymore - she doesn't think it will be a complication. We will have to wait until the surgery to see if the teeth can stay or not. She will need to stay at the hospital for the better part of a week, then home to be on box rest for a short time (poor Allie! MORE BOX REST) then out into a small yard for a time. Antibiotics, bute, ulcer guard etc etc for a little while. Keeping her nostril wiped out and clean and making sure she keeps as calm as possible will be the only aftercare I will need to worry about for a short time. Christine said she won't send her home with me until she is pretty low maintenance.
To get her to eat after she comes home from surgery I am to feed her whatever she likes - I predict that will be leafy green lucerne hay and chaff with Honey B. Worry about putting weight back on her when we can. I don't like feeding my horse junk food but you have to do what it takes in the end. I can get her back on track afterwards.
There will be LOTS of after-surgery follow up visits. We just don't know right now what will be involved until the surgery is done and dusted.
I can not wait until this whole thing is behind us and we are out of the woods and I can go back to worrying about normal things killing my horse like regular horse people do.