I do my quilting on a domestic machine and when I have the really BIG ones, I quilt the center of the quilt first, then I sew on the borders, backing & batting and quilt those separately. Really makes it manageable.
So if you can't find a longarmer near you who can quilt one this big, you might want to have the center longarmed and then do the borders yourself.
You're going to lose a few inches in the quilting - probably just 3-4" of those 77 if the quilting is big and open, but potentially a lot more if the quilting is small and tight.