The place is fantastic and you can walk it in a day up and down.
Avoid eating at the main square as they are going to rip you off, there are some nice restaurants in the alleys - ask around and people will recommend you.
Shop around for chocolates as you will find them cheaper the more you look.
Great beers!!! Great food, great chocs!
You can practically walk from the train station to the centre of the town in about 30 mins so no need for transport while there.
As for staying, hmm, can't recommend something specific because I can't remember the name of the place!! I paid around 70euros per night which might be more than what you are looking for. Google for hotels, keep in mind that you get what you pay for!