Your Macbook Pro has a written warranty that you should read. In the US, the Magnuson-Moss act is also relevant, you can read it on-line.
You'll read advice opposite of what I post below, refer to the two documents above if it's not clear.
1. You don't "void" your warranty by installing anything, regardless of what anyone on a forum, on the phone at Apple, or in an Apple store might tell you. Read the warranty, read the Maguson-Moss act.
2. If you have a problem with your Macbook Pro in the future, and Apple believes that a modification you made caused the problem, they can deny warranty coverage. If you replace your hard drive competently with an appropriate drive (similar interface, size, heat output, weight, and power draw), it is unlikely that Apple will believe the drive caused a problem with anything other than the drive or the drive controller.
Good luck.