Read the interior forum, if you take just a little time searching and reading you would be surprised at how much you can learn without asking a single question. I would suggest to start with a panel in the shape of the original then build a frame to hold your speakers, arm rest, etc. Then stretch fabric over it and resin it. Fiberglassing is relatively simple to grasp but becoming a skilled craftsman takes practice!!!
READ ME - Interior Door Panel (and more) FAQ - READ ME
fiberglass door panels, dash, center console, sub enclosure, amp rack
Hope this helps!