Quote: - I own a Metz 48 AF1 flash, I tried it on an mz-50 and they seemed to be communicating allright, how far back will my flash and film SLRs be compatible?
I cant help you on the metz, I don't use flashes and all I own is a once used AF280T and an old superlite II.
Quote: - I would figure not all models come with lightmetering?
speaking of Pentax cameras. you would have to go all the way back to an SV (1962) to have a camera
without a built in meter. of course as you get more modern the meter gets more sophisticated and automated. so this won't be an issue if you are only looking for K mount bodies.
Quote: Is there actually much difference between different models when it comes to the quality of the picture? In other words, should I focus more on what lens comes with the camera? Is there any noticable difference in quality when it comes to what film you buy?
the camera itself has no effect on picture quality in regards to its basic functions. of course how you use and utilize said camera and its features will certainly have an effect. this of course matters more with modern bodies, not so much with older manual bodies. what lens comes with the camera may or may not be an issue. are you looking to purchase a K mount camera? yes, yes there is. but I would be more concerned with the developing of the film and the ability of the person(s) you choose to let handle this task. as developing can have a huge impact on the quality of your photos.
Quote: - Are there any models that come with a focus-help for manual lenses (like my k100 does)? Or is this a bit of a non-issue since the viewfinders are large and bright enough for it not to matter?
more modern AF Pentax bodies I assume do have the same or similar type of focus confirmation for manual lenses like that of your digital body, however not owning any modern AF body I cannot say for sure. this depends on what model you choose to purchase. if you are looking for a body designed for manual lenses, then yes your viewfinder will be large, bright and easy to use concerning confirmation of focus. (typically with a split-image type of focusing screen).
Quote: - Something about film in general, can you change lenses while you're in the middle of a film?
yes, you can. the film is only exposed when you press the shutter and the shutter curtain opens. it is the same process with your digital. when the shutter is not depressed the curtain is closed and the sensor is not exposed. you can see the process very well upon purchasing a body. just open the back (with no film loaded or lens attatched) set the shutter speed to a slow setting,depress the shutter and watch the shutter curtain open and close.