Sounds like you've gotten all my advice but I've missed you and wanted to say hello.
I've frozen my own potatoes, purchased frozen mashed and tried refridgerated ones. None are as good as fresh made but all are much better than the powdered kind. I've also gone all 3 routes with home fries too and they hold up better in all cases. If you're not happy with the mashed, go for the home fries.
I've always been a meat & potato kind of girl and so living without these would be difficult for me, or maybe that's just the Irish in me rearing it's head. LOL
I hope you find something that works for you & that you have a quick, easy recovery from the surgery.