Need early retirement advice (health insurance etc)

So my company got bought out, and we're merging with them in a few months. I'm 57 (would have 35 years at the company in August) and, while there are positions available at the new company, I'm thinking I'll just do early retirement. My issue is I have no idea how health insurance works in early retirement.

A friend who retired early says he got his in the ACA marketplace, and apparently is getting a discounted rate because of minimal income in retirement. How does this work? If I just live off non-retirement funds as long as possible, does that mean I have no income other than interest and dividends, etc.?

And what about for the rest of this year. I have a good salary, and severance for my years of service is a full year's salary, so I assume I'd have to pay full price at least for the rest of the year.

Are there good retirement advisors I should be asking? How do I find one? My Fidelity advisor says I have plenty to retire now, but with a distinct lack of specifics with regard to how retirement "works".

Thanks!