From what I am seeing on this forum, the time frame will depend, a lot, on which branch you were in. Army and Navy seem to have a fairly quick turnaround on the paperwork and getting vets there new documentation stating they are now retired. Air Force is a different story. We have to wait for the survivor benefit briefing (SBP) and after that I haven't found anyone on this forum who has been passed this briefing. I received my letter almost a month ago and called AFPC per the letter. Just waiting on my briefing now.
From my understanding, if your VA rating is a 30% and you mil rating went from 20% to 30% it will be a break even and you will continue to get your 30%. You will now get the retired mil ID and able to use base for all the amenities a retired mil member. You can also get Tricare. But before all this you will need to get your amended DD214. I am assuming we will all be receiving the DD215 for this correct.