That is a Weber Spirit 700 (Weber 571201). I can't be sure of the year but mid 90s is reasonable. The serial number should be on the top right hand frame rail, tucked under the burner controls. Swapping out the plastic counter top surfaces isn't too hard but would require additional parts to accommodate wood (assuming you want it to resemble a Weber Genesis 1000). There are plenty of gassers with restored or replaced wood slats and/or counter top surfaces. Check out some of the restorations on here and search google, limitless possibilities. The ease of such a transition would all depend on how you want the final grill to look.
In any event, $20 makes getting this a no-brainer in my book. Good luck with the overhaul and post up pics when its all finished.