Did this three times on my head gasket repair, M104, to get it right..made all the mistakes and finally got the sequence perfectly! What I recall is yes, the u shaped gasket is green with a seemingly impossible fit..

I found instructions calling for the guide rail pin to be installed first, then the cast cover slid over toward the cylinder head over the gasket..WRONG! You must leave the guide rail pin out and then you can slide the casting with it tipped and slightly high, tipped with the top in so it catches the inside of the gasket and yet leaves the channel in the u free to engage without crushing..And then the drift pins pull the casting down as you push together..finally into square orientation and it will engage perfectly. Yes, just a dab of sealant in the gap area..THEN the guide rail pin with the interference fit is driven in with its zero clearance fit..Only after the gasket us snuggled into the slots. And you should have zero leaks for a very long time. (sorry I dont have quotes to the instructions that suggested the guide rail pin go in first..no time to reread the various sources..But it comes out first with a simple threaded bolt -no special tool needed- and some careful pressure..and goes in last the same..with a firm drive..)