Smoking lamb roast

[Ltheruler]

Hi, I was requested to smoke a lamb roast for a holiday dinner. I didn't know where to start and couldn't find much online. I will be using a large offset smoker. Any tips would be appreciated. What I'm most curious about would be what temp to smoke at, rub, marinade, how to trim, how to know when its done and anything else that would be useful to know. Thanks!