I've found your best bet is to always strip the old finish off that way you get a better finished cabinet. Also when in doubt visit a Lowes store I've learned alot by going there. If you run into the problem of tough water stains or previous finishes that don't want to come off all the way they have a bleach for wood to fix that also get some 120, 180 and 220 sand paper. on the final sand with the 220 all it takes is a ver quick light sanding too much will seal up the grain and the stain will not seal up as good if you need wood filler see if you can find famowood filler works really well just remember to try and match up the color to the wood. good luck and let me know how it goes. oh also if you use stain and then top coat it stay away from using urathane based clear coats they will turn a yellow tint later try a water based clear coat and if you can get ahold of a HVLP sprayer use that they work wonders.