front end comes off with the 2 top forktube nuts and the head nut. those 3 points off, then the top of the triple tree comes off and the rest slides out the bottom of the headtube.
plugging the decomp along with lots of other relevant important info is in the 505/1a performance wiki page I linked before. The decomp is unnecessary on sachs and commonly prone to failure - much easier to just nix that now than have it crop up later and cause confusion. Like it's so negligible of a difference in starting you'd never notice, but the issues it causes wind up being rather non-obvious and lead people to all sorts of other fixes, thinking it's too rich or too lean or timing etc, and its just another dumb leaky sachs decomp
1 good tire lever is pretty important, 2 is easier, 3 is useless. if you're good you don't need any, but 1 is easier and the second can be useful often. Good cable cutters are just something I like that saves frustration. you're likely to have to cut your own cables to adjust lengths etc - especially if you want this to look good, and having good cutters means it's a lot less likely to fray the ends, it's easier to get it cleanly where you want it and also easier to affix screw on barrels to the ends (aka "knarps") which you'll probably be using unless you're goin thru all the effort of setting up to solder your own cable ends, and even then clean cuts are pretty critical to success