Heya.
I overwintered my very first squees (Daisy, Luke and Bo) last winter and while it just about drove me INSANE, it was worth it. Yes, they wanted to be outside, but with them being orphans in October of last year, releasing them would not have set them up for the success they enjoy now. All three were successfully released in the spring, and Bo and Daisy still come to visit after establishing themselves in the local wild population.
As mentioned, Andy won't have a stash or a drey and the fact that he hasn't been building relationships with the wilds means he'll be on his own (the squirrels in my parents' yard will all sleep together in boxes that my dad mounted in a tree when it's really cold out).
Be prepared with lots of enrichment toys, careful balancing of Andy's nutrition and if you need any help or encouragement for the insanity that a tiny little critter will bring, I discovered that the people here are second to none when it comes to assistance from afar.
~T.