Just relax and have fun. Watch the smoker temps. If 225-250, they will go 5-6 hours easy. If over 250, 4-5 hours. If they are Thick, they will take the longer time. Try multiple tests for doneness. 1) Hold from one end, about 4 ribs in with a set of tongs. Pick up the rack. They should easily bend 90° near the end of the tongs...AND...The surface of the meat will split and fray. 2) Take your meat probe or bamboo skewer and probe the meat in several places. If the probe slides in with Zero resistance, you are done. Rest 10-15 minutes on the counter, cut them up and serve. Good Luck...
Remember...If you're Lookin' or spritzing for that matter, you ain't Cookin'!...Every time you open the lid, add 10-20 minutes to your cook time!...JJ