Welcome...
I'm 53 y.o., and I can't stress enough the importance of transitioning slowly, slowly... (Did I say to do it slowly?)
I used to run barefoot or in minimalist shoes until about two and a half years ago.
Last spring, I decided to start running again, and thought it would be no problem to go minimalist again... I (re)started my running very slow, but even so, after about three weeks my achilles-tendons hurted like hell and I had to quit.
A few weeks ago, I had the courage to start running again, went minimalist again (Merrell Vapor Glove), and started even more gradual than in spring. But despite that, after two weeks, those tendons started nagging again.
This time I decided to run in 'normal' running shoes (neutral, not too much cushioning, and as little heel-to-toe drop I could find). Luckily, after ten days the pain has gone.
I guess I will continue running in those shoes for a few weeks, and then adding a short session of running minimalist a week.
(Note: Since I'm female, I guess it's possible that hormonal changes over the last three years have had an effect on bones and tendons that make me more injury-prone for a while than male over-50 y.os, but I was really mad last spring that for the first time in my - relatively short - running carreer I had an injury, because I had gone too far too soon... Hence my over-cautiousness.)