A machine's brand name does not mean all its parts are composed of the same brand. Parts and pieces may have built through other brands. These other brands should still be compatible to the actual unit though. As mentioned on the paragraph above, choose what is best according to most users. You can trust the opinion of experts and professionals with repairs.
When you go to buy anything online you have to make sure you choose a reputable site and one that has a return policy, just in case the goods you buy are not right. You will need to look for signs that your chosen online store is safe and secure with the payment pages encrypting your payment details. Look for the URL starting https; the s on the end means it is secure. Another way to tell is the padlock symbol on the bottom right of the page. And don't forget to read all the terms and conditions first.