The key thing for me AG is to change one thing at a time. That way you know what works, and if something isn't its easier to spot. If you change too many things and get a problem its not always obvious what's not right.
One session a week to start for sure AG, and I wouldn't be too worried about sticking to one or the other either. My perfect four week cycle would have intervals, tempo, hills and easy. Two sessions a week would be great but I wouldn't be in a rush. I'm hoping to add a second harder session myself, but that won't be until next year.
MS, those legs are entitled to be tired. Just go easy for a week or two.
Good running slinger, that first two miles would have finished me lol. In Torquay at the moment as my daughter is playing football. McDonalds in a minute then to try and get a run in later. Had a lie in this morning...