The steering box is a lot easier to remove than it looks like... pop the joints out of the Pitman arm, loosen the square shaft connector, remove the 3 bolts, and it should come right out. I'd much rather do this work on the bench. Removal also lets you fully drain the box of fluid, so when you re-fill the system you will have ~95% new fluid (assuming you also drained the reservoir, and replaced the low-pressure hose, which I'd also recommend... along with ONLY using the OE gold-colored fluid, not red ATF.)
Anyway, Sixto, the late-style box (as of 02/1990) does not have provision for the locking tool... there are external marks for centering instead. Also, the input shaft seal is about a million times harder to change as of 10/1987... you need to fully disassemble the steering box on those boxes!
Click here to read the gory details. Note that there is 1 page for the early type, and 12 pages for the late type - ouch.
Click here for the Pitman arm seal replacement procedure from the FSM. It seems this is the same on all versions of the boxes.
