It will all be clear come during enrollment time. In a nutshell, it's the SAME process as when you were working. They send you material, you make your pick and make any changes, you submit your choices however it is they tell you to do that and it's done. Basically you'll be selecting COBRA for 2017 which will be an option for you. Nothing to worry about.
I believe it's the same process when it comes time for us to use our last 6 months (Jan-Jun 2018), only we'll be selecting IRMP IF you want to use the $6,102/single or $12,098/family extra money they gave you. That money is NOT treated the same as SERMA and is its own line item in My Health Benefits account. SERMA you can buy your insurance on the open market, that $6K/$12K can ONLY be used for the way more expensive IRMP.
What I don't know since it's only good for half the year... is what happens come July 2018. I'm sure that will become clear closer to that time. Obviously you'll need to find a plan on your own, what I'm unsure about is losing COBRA considered a "Qualifying Event" so that you change your insurance carrier (to get out of the extremely expensive IRMP for 2H 2018). Had lunch with a retiree earlier this week and he seemed certain it is a qualifying event. I don't think so but sure hope he is correct! Will find out probably Q2 2018 to give people time to figure that out.
I don't think Intel is going to leave people in the dark for the 2 years we're still under their wings. You'll get material explaining what to do next.