Hi @Dothemo
I had a year off (about 5 years ago) when I was being diagnosed with BPD. I have to say I was terrified to go back but after the first few days it was like riding a bike and my confidence returned quickly.
To be honest I feel working makes me mentally healthier, it keeps me in a routine, it gives me a reason to get up and not let anxiety and depression take over. (unless I let it)
You will be fine, dont question yourself just go and ask as said before if you are unsure. As a HR manager I know the first day is the worst, you dont know the people, you dont know the culture, but it all falls into place pretty quickly. Also think of it as a new beginning, no one knows you or your MI, its like a clean slate!
Goodluck 