White smoke means steam, blue smoke means oil burning. Sounds like the head gasket is done though. Blowing tons of white smoke, runs like crap, probably has some history of overheating too. Search around in here and you will find MANY posts about blown head gaskets. In some cases the head will crack along with the blown head gasket, but you can't tell on that until you get it apart. The single best tip I can think of is to wire the timing chain to the cam sprocket so it can't move, then unbolt the sprocket from the head and leave it (the sprocket) with the block when you remove the head. This makes it so you don't have to worry about getting the cam timing back together right, because it won't move.
I kind of disagree with mytmouz on the Haynes service manual that you can find at most parts stores for the LUV. For a Haynes the LUV book is really pretty complete and would be a big help in getting started working on the truck. Of course a factory service manual is much better, but I wouldn't slam the Haynes or Clymer shop manuals.
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95 Isuzu Trooper Daily Driver
86 Isuzu Trooper reliable backup
77 LUV 2wd stock beltway blaster (resting)
79 4x4 LUV project: 2.6L, 5spd, 31s (eventually)
MEPR: Man, my 4x4 makes all other LUVs look good
