1) Yes, you need a restart. Anytime during solution , if you leave the /SOLU module and come back in you need a restart. In a transient thermal analysis at the first SOLVE command the rdb, ldhi files are created. Then the .rxxx files are created during solution. All of these files are required for restart.
2) You cannot add new elements to the model in a static/transient restart. So adding new surf152s will be a problem