I never kept my XL1S long enough to have things like the EVF go out of adjustment or start to die, Rayn, so I don’t think I’m able to help you much with your question. If the footage looks good as shot but the EVF is showing it differently then I’d suspect it’s on it’s way south. You might try unplugging the EVF connection and then have another look. You could also find someone else that has an XL1 and try their EVF on your camera. If that one looks good then…….
You can also go to the Canon web site and download a .pdf version of the manual if the camera you’re thinking of buying didn’t come with one.
Sorry I couldn’t be more helpful.
– Don