re the gaskets...
going on my experience with an 1150 and a 1200, both roadsters. the gaskets are made of a hard plastic material, nothing soft. They last. The torque values for the bikes mentioned were like 8 and 10 nM. In fact, on one of the bikes, I think it was the 1150, I replaced them after 10s of thousands of miles for no reason other than "just because they were that old," and had some buyer's regret. It seemed to me that the old ones fit better than the new ones because, I thought, they had settled in and took the shape of the small imperfections of the cover and base. I ultimately saved the old ones, and they still hang on the garage wall. Neither the new ones nor old ones leaked. Both old and new looked the same condition, the new ones did not look "new" nor did the old ones look "old."
I am "assuming" that the material for the GS is the same, and the torque values are similar---someone please correct if that is an incorrect assumption. I have not yet removed on my 16 GS so can't comment on personal experience with it.
Re the brake flush
The brake flush is on the list for the 6k service. In the past it was just "inspect," but on the newer bikes the FIRST 6k service states clearly "replace." Subsequent it is time and inspect.
re the GS911
The GS911 does not aid in the brake flush, but part of every service is to read the fault codes, which the GS911 does. It's pricey, but addresses the "peace of mind" dept nicely. Example, after a recent trip, I started having the experience of the bike not starting on the first throw of the starter. Also, I noticed at slow speeds she behaved sluggishly (like a pig with distemper) when navigating tight spaces, made the actual handling tricky and I almost went over on a simple neighborhood turn because of it.
I thought maybe it was some bad gas, from somewhere in a derelict gas station in NE NM, only had 86, and I only put in a gallon or so. When home I put in some seafoam and it corrected the issue so far I think--ie handling and power like new now. BUT...I wanted to see if anything untoward was going on, so I slipped in the GS911 and ran the fault codes, and all was fine.
--->>> Peace of mind.
Aside: for years I knew of the GS911 and because it's pricey ($350 ish) I resisted. When I got the GS, I bit the bullet and got one when I took delivery-it's price paled in comparison to the bike's and the WAF (wife acceptance factor) was easier at initial outlay than later. I am really glad I have it though, admittedly, it does far more than I understand. Just to be able to read the fault codes is worth the price. It eliminated the trip (75 miles x2) to the dealer for the 6k and 12k service as it was the only "service" I otherwise could not perform. And my time is cheaper than the dealer's, and I enjoy getting to know the bike.
I REALLY wish the GS911 could turn on the Dynamic Brake Light. It cannot, it seems.
If some euro guys have a hack for that, please post!
so i dont know. 
