Here is a forum thread we had about 3 weeks ago on the same subject. If ya want, give it a read and then follow up with questions in here.
http://www.smokingmeatforums.com/for...ight=pork+loin
Your daughter picked a good cut of meat. It is very versatile and as your skills increase, you can do sooo much more with it. We have threads in here of master chef's butterflying loins and stuffing them with some interesting things.
There are several ways you can finish up a loin, but for the most part, I like to indirect grill mine. I'll try to give ya the quick and easy on it, and you can ask any questions you might have. I'm sure others will pitch in ideas too.
Since this is your second smoke attempt, I'm gonna keep it easy. You can modify this any way you like.
Preparation
Rinse tenderloins well with water and pat dry. Drizzle lightly with EVOO Sprinkle with kosher salt and freshly cracked black pepper. I add some smashed garlic cloves on top and then cover and refrigerate for about 4 hours. Keep in mind, this is a simple to follow recipe and at anytime, you can go more advanced if you are comfortable with it.
Some people will marinate this cut, as it is super lean. Cooked correctly however, this meat will be juicy and flavorful. If you are going to smoke this cut in a smoker, maintain a temperature of about 225-250 and spritz or mop with a mix of 3 parts apple juice, 1 part water about every hour.
Some people will also wrap these in bacon to maintain moisture. Whatever you want at this point can be done. experiment a bit and share the results with us.
You want to carefully monitor the inside temperature with an accurate thermometer. When the loin reaches 145 degrees internal temperature, remove it from the grill and wrap it in foil. You may again mop or spritz before sealing the foil.
Let the meat set on a cut board, wrapped in foil for about 15-20 minutes. This allows the juices to redistribute and the internal temperature to rise to 150-155 degrees which is well above the 137° necessary to kill any trichinae. This should produce tenderloin that's juicy, tender, and safe.
This is also a personal choice. Some people will cook their tenderloins to 160. I have found that 150 is perfectly safe, within USDA and Pork Council guidelines and ensures a tasty, moist piece of meat. We don't want to dry it out or separate the grain of the meat.
TIPS: Instead of the last mop of apple juice, try an apple or orange marmalade or jelly and brush it on before sealing the foil. Be creative.
I hope you found this helpful, make sure to check back on this thread several times, as you are going to get a lot of good advice and tips on this versatile piece of meat.