Hi Jimbo, welcome to the world of Pentax and this forum. You will enjoy the camera and the support on this forum, a great bunch of people in my opinion.
As to the best editing program, most cost money and they all have their particular advantages and disadvantages. You can download trial versions of all of the commercial ones, Corel Paint Shop Pro X2, ACDSee Pro 2 and Adobe Elements and of course Google's Picassa which is free.
My personal choice for day to day post processing is ACDSee Pro 2, it has great cataloging funtions, and a very strong editing feature set, but I fall back to PSP X2 when I need some really heavy fixes.
A good one to try as you get totally involved with this great technogy, I just discovered it lately and find it very easy to use is FastStone.
This is also Freeware for home use, and is the absolute best viewer for PEF, DNG, and JPG's I have ever used, and all info is available as are all controls just by moving the mouse to the Left, Right, Top or Bottom. Try it from
FastStone Image Viewer, Screen Capture, Photo Resizer .../
Good Luck... and have fun.
Phil