Couple of suggestions:
1) use a cleaner/plastic prep made by SEM to ensure that any grease, ArmorAll, crud, etc. is completely removed before you prime or paint. SEM makes a very complete line of products specific to refinishing interior plastic & vinyl surfaces. I've had excellent results using their products over the past 15 yrs, as long as I followed their recommendations completely. Also, I'd suggest that one use the entire 'system' from whatever manufacturer they have chosen, to make sure that everything is compatible. . .
2) purchase a Helms service manual for your '98. You should be able to locate a used one at a fair price on eBay (or even on this Forum). You'll pay for the cost of that manual with the $$ you'll save because you didn't screw up and break a part trying to remove it without specific 'how to' instructions '. Some of the parts - such as the plastic piece that fits below the radio and above the center console - as an example - are downright tricky. Ditto for the parts around the HVAC controls and the stereo. (or go to a pick-a-part type of auto-wrecking yard and practice on a junker !)