Personally, I don't like bed lined interior floors. I like comfy fresh carpet, mainly because of the heat and noise barrier, and because I don't generally like stripped down vehicles. No carpet was standard on the custom deluxe trucks.
As far as dying the interior, so far so good for me. I'm using SEM paint, which is probably the best stuff out there. THe question is, is how good your dash and door panels are. If they are pitted, crusty, and smudged, the paint may not take well and go on smooth. It's just easier to start out with new stuff IMHO.