Fortifying and oak aging would seem pretty requisite. Sounds hard to do depending how patient, or how picky, you are. I bet one could get pretty close to one of those less expensive domestic ports that have things like "Great for Cooking!" derisively present on the label, but duplicating a good tawny or vintage port from Portugal is going to be tricky indeed. The kit may be a good bet, then fortifying with a youngish brandy and using some sort of mild oak product for aging.