To get the yellow out, try soaking your shirts in OxyClean overnight before washing. The heavier yellow, the more it should soak. Helped restore a lot of my dress shirts but I tried it on some old undershirts that had caked on deodorant for years of wear.
Another quick tip. If your shirt is unpacked and has some wrinkles in it, hang it in the bathroom, turn the hot water on and let it steam for a bit. Just make sure you close the bathroom door in hotels, if not, I have had the fire alarm go off. Pants with wrinkles? Same thing works, but hang them upside down so the waist hangs at the bottom. The added weight pulls the wrinkles out faster.