As far as chipping goes....in my opinion there is NO downside. Diesels get the most amazing gains from aftermarket software...if you decide to do it...you'll be VERY impressed. It can present a problem with warranties...although technically they "can't void your warranty on something that breaks unless they can show it was caused by the installation of the "chip". (See Magnusson-Moss warranty act) but some dealers WILL use it as an excuse to not cover something and in that case you'd have to find a dealer that is "chip friendly" (more and more every day) or take em to court. ie; If they deny you coverage on your cooling system because you have a chip...you'd win.
1998 K2500 Suburban, 9" lift, 37" Baja TA's, 4.56's, 16k Winch, Lots of mods