There are a lot of 122s,1800s and 544s running around w/o w/s chrome because it is a tedious job to reinstall,It is very doable but you must have an extreme amount of patience.I have a green book that will tell you there is a rope trick,but I have had no luck using the rope to put chrome back on,though the rope does work well for putting the unit back in the car.
First the glass should be outside facing up on a cradle.
Next the rubber goes on the glass.
Next you will need to start working the outer perimeter of the rubber down while pushing the chrome into its groove,the chrome should be clean with no debris,and the groove in the rubber should be well lubricated with either liquid dish soap or spray silicon lube.you have to keep pulling and rocking the rubber kind of away and then back toward the chrome really feeling it with your thumbs,you should be able to work the rubber,stretch it when you need to it is difficult especially with a new gasket(an old gasket will have the form and memory whereas a new gasket will fight you almost all the way),at any rate as you gain distance fitting the chrome in place,you will need a very patient assistant to follow behind you and hold the chrome from popping back out(it will try to pull rite back out as you go)you could try to hold it with tape but the lubrication compromises the tape.I'm telling you this job is a PITA I have done several of them,I hesitate to suggest the aid of an assortment of pliers,hooks and picks because they can often do more harm than good,but they are good to have on hand.The last time i did one of these I walked away from it twice to cool off and then finally went back at it, I think it took me about 3.5 hours.hopefully someone here knows some short cuts.I can tell you though if you focus and stay persistent it will go together.
good luck