The kit is like 25 bucks it's a 1 beer job.
Mine had one installed by the dealer no charge for parts or install. I also got my tunnel protectors and studs for no labour cost. And either 300 towards accessories or a free belt and 2 jugs of oil and first 500 mile service free.
The one nice thing with the poo is 2 side panels with easy clips and then 2 clips, unplug the harness and take the hood off. Pretty easy to get your arms in there to clean the engine and belly pan too.
Does the 850 have electric start. I thought they came with a 12v plug. That is pretty dumb if they don't but they have a charging port for the battery I see.
The donut will seal up fine. Mine did the same thing last year and I just clean it up after 50 miles. There are 2 plugs for connecting accessories. One under the dash and one in the velcro bag where all the connectors are.
Sounds like you got a shitty dealer.
Nice! We have a ride planned for March 7-8th with a few members and some American friends hopefully. RAP tour if the weather is good. You sound join us if it happens.