Some Elbo Grease
You may have already got the answer, but I will post here anyway. There are a couple things to consider. First, since you don't know exactly what was applied to the cabinets, you probably don't want to short cut the work and have to redo it after everything dries. Do you plan on staining or painting for your new finish. If you plan on painting then you should be able to get by scuffing up the existing finish then priming and painting. Now if you want to stain the cabinets you will want to start with a clean slate. There are many different kinds of strippers out there, take a walk down the strip I'm sure your bound to find a couple within seconds (haha). I have used a Citris based non-toxic stripper and it worked pretty good. I can post the product info later. The key is use the same for the fronts and the boxes for consistency. once you strip you will want to sand with 120 and 150 with the grain. Apply the new stain/tint then sand with 320 before applying the final top coat. The key to the product you use will be the application of the product. If you will be rubbing it in (my recommendation) you can choose any stain really. If you plan to spray on you will have to talk to someone else cause I know nothing! All I know is you have to take into consideration the evaporation and some other things when using a sprayer, not my forte.
Hope this helps. I am in the middle of doing my cabinets right now.