These guys are right on as usual about the grade. We did some Prime grade rib roasts around Christmas and they were awesome. Still have 2 in the freezer. Paid 9.99/lb for Prime and well worth it. So if yours is prime, that is a good deal as Bob and others have said. A good price for Choice.
I don't have any experience with your style smoker, so can only give you some general advice. Keep your rub simple - not like pork. Rosemary, garlic, evoo, S&P, etc. Don't want it to overpower the meat.
I sear mine before I smoked. Got that idea from the forum - RonP I think. Nice flavor.
Finally, don't over cook. We usually cook to 120 becasue we like rare, but I have cooked them to 130 and still had them plenty rare-med rare.
Here is a post I did a few weeks back:http://smokingmeatforums.com/forums/...ighlight=hasty
Do a little digging in this forum - search on prime rib - and you will get tons of ideas. There is no "one right way". Good luck.