Hello :) That'll be a lovely trip! Good news is St Andrews is not a city or even a big town. I think it's formally classed as a small town. So unless you really want to visit the big supermarket on the edge of town, St Andrews is basically three streets lol. You'll easily do it in a couple of days. It's a beautiful place to just walk around and see the sights, spend some time around the pier and the golf course. There are ruins of a castle and an old cathedral which are all fairly central. There's a few museums - Wardlaw, St Andrew Museum, I think there's a golf museum on the course. A botanic gardens which I never actually went to but I heard it was nice. In terms of food I probably can't recommend much because I haven't lived there in a decade so the places will probably have changed but one place I know still exists and I dream about it regularly is The Tailend. It's a fish and chip restaurant and it's the best fish and chips I've ever had. You could also nip to some places near by. Transport links aren't the best but Dundee has a branch of the Victoria and Albert Museum which is supposed to be good. Hope you have a nice time :)