Mutty, welcome to the world of Pentax DSLR - you'll be pleased, and one of the reasons is that there is so many choices available to you.
Robar gave some good advice. One of the things to remember, however, that zoom lenses are a trade-off is some regards. They do everything in their range well, but in general not as sharp as a set of prime lenses. There are trade offs with each approach, and much of it has to do with what kind of photography you want to do, and for what purpose. I have some primes and some zooms, and love the flexibility of the zooms, but use the primes for specific things like nature/animals, portrait work, etc. I recently sold a Sigma 150-500mm I had because throughout it took very good pictures, but not often great pictures.
The beauty of Pentax is that you have a whole world of possibilities out there. With adapters, there are myriads of pretty good M42 (screwmount) lenses available on eBay. Let me share just a couple of things I have learned with my lenses.
1) As far as zooms go, I love my Pentax DA 50-200, (very light, very quick AF), Pentax 28-105, both FA (autofocus) and A (Manual Focus). I also love my Tokina AT-X 100-300 Manual focus lens. I also have gotten some great shots with my Tokina 19-35mm AT-X AF. I have found that the images I get with Tokina lenses tend to be slightly underexposed, but very rich. I also have 2 Kiron zoom lenses, and against my better judgment, am telling you that they are among the best both optically and mechanically. Because they aren't one of the big lens makers, they often get overlooked and lumped in with some of the cheaper consumer lenses, but results and reviews on Kiron's are universally positive. Just don't tell anyone that little secret, OK?
2) In terms of primes, my favorites are my Super Takumar 85mm, my Sigma 105mm Macro autofocus, and a couple of German and Russian lenses, (anything by Carl Zeiss Jena) and the Russian being the Zenitar 18mm fisheye lens. My big old Pentax 400mm M42 lens also does a wonderful job.
I find myself increasing using the manual focus lenses, because of the control and the feel associated with setting aperture, focus, etc. When taking shots of the grandbabies, the AF lenses come out so I can pop pop pop with little delay.
Enjoy your upcoming experiences, and I hope these comments help.