Hey, late already welcome to the AMR world. hahe, kidding aside if coming from 121 better know your 121 stuff, it'll be breeze. If not, study your basic IFR rules. If they ask you to brief an app, use the briefing strip, include the MSA, make sure brief the available runway length, and highest obstacle. That is a standard Eagle brief. Maybe you'll impress them. Which base you picking. May I reccommend BOS. good luck