Newbie - Cooking/Storing Meat

I'm not a very knowledgeable or experienced cook, but trying to change that! Also, I've been vegetarian for the past 5 years or so and transitioning back into eating some meat. I really don't know how to cook/store meat so need some help in that area. Specifically, one of the things I'd like to eat is pork tenderloin, which my mom used to make and I really liked. She used the prepackaged/seasoned tenderloins that you can get at the grocery store. My biggest question is - since I will be cooking just for myself - how to deal with leftovers. Can I reheat the leftovers over the next week to eat? Can I eat it cold (like sliced on top of a salad)? Thanks for any tips!