My '02 Horizon has the same problem, and I am thinking about removing the vinyl, the old deteriorated foam, and replacing. The foam can be bought in any number of places, including just about any fabric store. It's just that I'm not an upholsterer, but it might not be too bad a job.
I did see one motorhome, where the guy's wife just sewed a new, padded dash cover, cut to shape, and just layed it over top the old dash vinyl. It actually looked really good.
on edit: In case you didn't see it, smlranger did a really nice job of making a new dash cover. Here's a link to his thread:
http://www.irv2.com/forums/f101/repl...ng-110877.html