Easy side: Cube 2 large sweet potatoes (about 2 lb.), and toss with 2 Tbsp. olive oil. Bake at 425° for 25 minutes. Remove from oven, and toss with 1 tsp. salt and 1/2 tsp. pepper.
Preheat grill to 350° to 400° (medium-high) heat. Remove silver skin from tenderloins, leaving a thin layer of fat. Sprinkle pork with salt and pepper.
Drain pineapple, reserving 1/3 cup juice. Grate zest from limes to equal 1 Tbsp.; squeeze juice from limes to equal 1/3 cup.
Bring reserved pineapple juice, lime juice, zest, marmalade, and next 5 ingredients to a boil in a saucepan over medium-high heat. Boil 3 to 4 minutes or until slightly thickened. Reserve half of mixture in a bowl.
Grill pork, covered with grill lid, 10 to 12 minutes on each side or until a meat thermometer inserted into thickest portion registers 155°, basting with remaining half of pineapple mixture. Remove from grill; cover with aluminum foil, and let stand 10 minutes.
Meanwhile, grill pineapple slices 1 to 2 minutes on each side. Serve grilled pineapple and reserved pineapple-marmalade mixture with grilled pork.