I'd think that a 2002 IP would be under warranty still - HT's should last 20 years or more. Have you called IP?
The only problem with plastic tanks is the lack of baffles to prevent sloshing around. If you are handy with tools you could build a custom tank with 1/2 inch marine ply, encapsulate it in epoxy with a 6 oz fiberglass overlayer inside and out - and include baffles and it would last longer than your boat. You could probably do that for 1/4 the cost.