Cool bike. Hope you'll post progress pics.
Likewise, I got a cruiser bike several years ago and started riding again after a long hiatus. The one speed was tough with the hills here (and my weight and noodle legs lol). So I converted it to 3 speed. I had to replace the bottom bracket as the coaster brakes were toast and it was making a clunking sound-- I think it has a lot of miles on it. But it's a lot of fun and much more comfy to ride than the MTB I had way back when.
Best of luck with your project and new fitness regimen!