Find out if your state has a local Senior Advocates program to walk you through the Medicare process. Also look into local insurance brokers that specialize in Medicare.
Do not put this off as any deadline to file you miss will penalize you monetarily for the rest of your days.
Expect to pay about $184 per month out of pocket for Part B. A decent supplement plan averages an extra $220 out of pocket per month. Avoid Advantage plans like the plague. A good Broker will tell you why.
Part D prescription is a requirement even if you don't use scripts. Cheap plans can be found for a few bucks.
Dental plans are the ki-ler - yes, cheap to start but could never find one that covers anything other than a routine cleaning for Year Number 1. If you need filings, crowns, etc, get them done while still employed or wait until the 1 year hold period had elapsed.
Good luck, figuring out retirement, Medicare, and Social Security are not for the weak of
mind.
Last thing, when I applied for SSA and Medicare I needed a signature from HR affirming I had health care through the company since age 62.
Took 5 weeks to track down an actual life body in HR. All the "call these numbers" either got a clueless aLight contractor in Arkansas or worse, 19 year old call center guys in India asking for my Social Security numbers. NOPE. Ain't doing that sport.
Almost ended up just forging a name I got from the company directory, before some HR dude eight states away agreed to sign the pdf after I threatened to spam him every day of his life.
Good luck.