Good call. I think the MZ-10 is a fine camera and a bargain with the film and lenses.
I haven't used the Pentax 28-200. It's reputation is that it is OK -- but not the sharpest. Don't worry about that, it will be plenty sharp. On the other hand, I have experience with a couple of copies of the 35-80, and it is a terrible lens. I could see how soft it was in the viewfinder! But that's fine because you've got the 28-200. Eventually, I would recommend one of the Pentax 50mm autofocus lenses... the F or the FA, in any speed. Just buy what you can find cheapest. The focussing screen on the MZ-10 is optimized for slower lenses and not for manual focussing. I think you will appreciate having an autofocus 50mm.
The best recommenation I can make regarding shooting black and white film is to buy a lens filter. Get a red, or at least a dark yellow. The effect reduces haze and improves the rendering of skies enormously. Ironically, a filter might cost as much as your camera! But it is worth it.
If you want to shoot with flash, the MZ-10 can also take advantage of the last-generation of Pentax TTL flash. Since they have been deprecated by the advent of P-TTL flashes, the TTL flashes are often a bargain. Even the simple Pentax AF220T will give you a proper TTL flash with bounce. You could also add a no-name brand TTL flash cable and move the flash off-camera.
Another recommendation for the MZ-10 would be the accessory battery grip. The FG battery grip works on most of the MZ-series of cameras. It allows you to use AA batteries. The MZ-10 is a small camera, and if it's too small for your hands then you will enjoy using it with the grip attached.
Have fun with your new camera -- it is already a capable tool even without any of the other nonsense I have recommended!