Hi Lzel,
1. Crisp and clear are pretty subjective. The Pentax 18-55 is considered a very good "kit" lens compared to those offered by other brands. With any of the new models, the 18-55 stopped down some should produce images that can pretty easily be printed to 16x20 without visible lack of resolution.
2. I'd suggest you visit a store that sells a lot of TVs. Tell a salesperson that you'd need to see the difference between the two resolutions to decide what spec in a 42" TV you'll be getting for your mother's next birthday. I'm sure they'd be happy to demo this for you. I assume that I don't need to tell you not to buy the TV
3. I agree with Mark, it's doubtful that the replacement for the Kx will have a magnesium body. This is usually reserved for the higher end bodies from any mfg. Pentax's plastic over stainless framed bodies have always been very solid and sturdy, and have never been considered "flexy", toylike, or cheap as some competitors have been and continue to be. I like the metal body of the K-7, but have had no complaints about the feel of any of the previous DSLR bodies.
Scott