hi, I would recommend to focus on material edits with 3DSimED only.
you can save the properly working material library from the original GMT into a file set with 3DsimED (Save Materials), load / import your new mesh into 3DSimED and load the original material library back. this will replace the whole material settings back to the original one. it just needs to have the old and new mesh materials same name.
with 3DSimED you can do various material magics like copy and paste the whole setings incl. current texture file relations or just the current mesh shader material properities, you can replace / assign materials on selected mesh polyons and so on.
therefore once you buildup the 3d files in 3DSMax, exported as 3DS, X file, GMT or whatelse, you can do all the rest with 3DSimED only