refinishing kitchen

Could anyone give me some advice on my current project, which is refinishing a friend's kitchen? It looks like a light oak with an original polyurethane finish and is about 20 years old. It has quite a bit of grease and grime at the handling areas but is mostly in pretty good nick and needs a new coat.

I've been reading most of the postings and got totally lost in all the info.
My questions are:

• What is the best way to clean the cupboard doors?
• What is the best product to use (I admit that I have my doubts about using polyurethane)?
• What is the best/easiest way to apply it?

Any advice is appreciated,
Ozcruiser