Lamb is good, you're gonna like it!
I've never seen breast, but I've smoked legs, I usually poke holes in the meat and insert chunks of garlic, dust with salt and pepper, fresh rosemary and thyme, wrap in plastic and refrigerate over night, I smoke them at 210°-220° until 140° around 3 1/2-4 hours, I put a foil pan with beef broth and onions underneath to catch the drippings, makes a good juice to serve over the meat.
We like the taste of mint sauce with our lamb, you might like it too.
Mint Sauce
1/4 C chopped fresh mint leaves, stems removed
1 tbs sugar
1/4 C vinegar, we use a white wine
Place vinegar and sugar in a pan and heat until the sugar is dissolved, remove from heat let cool slightly and add mint leaves, you might have to add more sugar or less vinegar to suit you tastes.
Enjoy your smoke,
Gene