I'm in the "get a whole new rig" category, too. First, your engine is old and the company that made it is out of business. You don't know how long parts will be available. Second, most boats today are sold as boat/motor/misc. equipment packages and getting just an outboard for re-powering is actually pretty tough right now. Even if you can re-power, it will cost a lot. Larger outboards are crazy expensive, and then you'll have to purchase all new controls and have them installed. You might also have to change out your steering linkage, too. When you look at all those costs vs. the cost of a completely new rig minus what you might get for your current boat it might not be that much more just to go with the whole new rig.
You'll love the new 4-strokes. They are now as light as what comparable DFI 2-strokes used to be. They have far better acceleration and top-end performance than the 4-strokes of old. They get great gas mileage, and I'd doubt you'd ever wear one out unless you run it hard 5 or more days a week every week. Four-stroke car engines can go 200,000 plus miles now pretty regularly, and 4-stroke outboards will go a long ways, too.
Ed Gerdemann