I did my tcase fix myself, I'm a welder so that helps. it's a magnesium case so welding know how is critical, your cheapest bet would be to remove the tcase, just use a floor jack. open it up, remove housing where hole is, give it to a good welder, be sure to tell him it's magnesium. then inspect the tcase for worn/damaged parts and replace as necessary. when I first detected the hole I removed right away and repaired the hole, cost me about 100bucks in parts, gm has a updated clip for the pump, I wouldn't bother with the aftermarket, pump plate assy's (kennedy diesel, etc.) They are not necessary IMO, the gear guy I deal with says after the tcases get the updated 8 dollar clip, he never see's them again. I will refer you to my gear suplier : Border Parts, 3875 Bancroft Drive Spring Valley, CA 91977 (619) 461-0171 the guy is a whizz. At very least I would remove and open to assess the damage. Good luck.
04 silverado 2500 hd crewcab 4x4 lb7 FASS platnum lift pump, Nicktane adapter running cat filter, air horn port mod, everything else stock.