Steering Gearbox Seal Replacing...hard?
 

I have had multiple leaks in the steering system on my 1984 500SEL (euro). Replaced high pressure and return lines, changed seals on pump (main leak was from round pressure plate oring on back), and tightened fittings to box really good. It is still leaking a little from the gearbox arm shaft seal on the bottom and the coupling shaft at the input side. Also, the coupling shaft side has a flat cover plate with a regular gasket. I bought the seal kit, cover gasket, new coupling, and idler arm rebuild. I searched in this listing, and found some people describing what I am about to do as not too easy. I have the manual and can figure out the obvious "put everything back the way it was" stuff. The steering itself is absolutely fine with the exception of a little extra play (idler arm bushings and/or coupling i hope), so I am not worried about dimensioning exact wear. So what do I need to be careful of that may not be obvious? I am hoping $100 for seal kits and rebuilds will keep this box going for a few years until a total replace is warranted.

Many thanks.