Visa Run To Cambodia

I am in Nakhon Sawan and need to do a visa run in the next few days, I gather that there is bus which leaves here at 10pm most nights. Can anyone give me any information about what I need to take or what I will need for the trip. I obviously will need to take my passport anything else for the immigration officers? I expect there is a fee to pay ( 500bts at Mae Sot ) how much? How easy is it to use bts in Cambodia? To ask how much money to take is like asking how long is a bit of string, but if anyone has got any giude is would be useful I am not intending to go on a shopping spree, drink Vats of wine or eat vast quantities of food, any helpful advice would be gratefully recieved.