Welcome (back) Studio20! The K20 is a very good choice! The lens combo of course is a matter of what you have to spend and what you want to shoot. I started with a K20+manual lenses, both k-mount and M42. For the latter you need an adapter - be sure you get the genuine Pentax adapter. Out there on the web are many *many* great manual lenses for almost nothing, so you can easily try which lenses you like. And autofocus? Well, I only have one, the Da 70/2.4 Limited. I would recommend it highly, but if you would buy all lenses people on this forum recommend, you would be broke before the end of the month...
Enjoy these forums, you'll like them and you will find info on all those lenses.....