In terms of the gibbs, i would cut yourself a secion of shim stock that will allow you get your adjustment back on teh gibbs.
tramming the head left to right should be done, but i would do it after you tram the column. get your cylinder and indicator and run the whole head up and down measuring deflection against the cylinder square. then loosen the head bolts and add shims accordingly. now tighten the column to the base and recheck tram. keep adding or removing shims until you are happy with the tram.
the head tilt can be ajusted but loosening the 3 bolts that hold the head. now retighten them but only snug. now check to tram left to right on the x axis table.
now check the front to back positions against the table as well. for this youmay have to add shims under the head and between the slide.