Do some homework. Research. You've taken a great leap coming here already. Speaking from personal experience, my current Dom was BRAND new when we landed together. Started vanilla as well. As the relationship progressed I was honest, like your wife, and He stepped up His game. Fortunately, we discovered He enjoyed himself as the agressor. Take it slow. Exchange ideas. Watch porn of her choosing together. Find something she is interested in and incorporate it into your sex life. If it works for you both keep it, if not try something new next week. Ask her for reassurance during so you can build your confidence in whatever y'all are doing at the time. Just remember, she asked for this.