If your cabinets are solid wood, this is not a problem at all, and it will save you a lot of money when compared to purchasing new cabinets. Simply remove the doors and drawer fronts and use paint-stripper (in a well-ventilated area) to remove the finish. Fill in any scratches or dents with wood filler, and then sand the surface. You will want to sand everything down, and the best way to do it is to first use 100-grit paper, then work your way through multiple sandings up to 220-grit paper. The final product should be extremely smooth. Once you apply a sealer, your cabinets will now be ready to stain, and depending on your choice of stain, they can look like entirely new cabinets.
If the cabinets are fiberboard or another material that is not hardwood, your only options are to replace the cabinets or to apply a veneer. Veneers can look great, but are not identical to real wood, and can’t be sanded or re-stained.