Tiling over painted kitchen walls

I'm a total novice. Have never done any tiling but would like to tile the lower portion of my kitchen walls. I have an older house with plaster and lathe walls. Currently the lower part of the walls looks like tiles but I believe it is just the plaster made to look that way. I have an 8"(apprx) oak baseboard that runs around the entirety of the kitchen and there is a also 3" oak chair board that runs approximately 4' from the floor. I would like to tile between these wood borders. If I use some kind of backerboard, it would nearly cover the edge of the woodwork and I think look weird. CAN I TILE DIRECTLY OVER THE PAINTED SURFACE OF THE WALL? Is there a product to use that works better (and is simple) than others to us to attach the tiles? And, when setting these tiles on a wall. Where's the best place to start out. An upper or lower corner? Also, I have a kitchen countertop (formica) that was replaced about 15 years ago. The old counter was taken totally off and rebuilt. Then formica placed on it and the splashboard. How difficult would it be to tile over the formica? I have heard this can be done without problem. Please speak in very simple terms. I'm anything but stupid but when taking on something I;ve never dealt with before. It helps! thanks, Kim

Kim, before you go any further, you might want to find out for sure what that wall is.

I also think you should find out what conditon theses walls are in too, from my experience with lathium plaster is it has the tendency to crack overtime especially with setting of the house and any cracks which occur in the plaster will cause cracking in the tile as well. As far as tiling over formica goes it can be done under the right circumstances but I don't recommend it for someone like you who does not have a lot of experience with tilling.