In most ways we cannot create a bio-mechanical human that works better than the human body as whole does now. You feel that way because you can repair what you build and call it better because its faster (sort of), but one of the biggest hurdles we have not been able to overcome is self-healing. In theory we know with nano technology we can create some self-healing objects sure, but in no way are we even close to being able to create a being that is improved and can heal itself back to original form when damaged. That's one.
On the other hand, your argument is faulted by assuming that immortality is a good thing, or being able to live hundreds of years. Maybe it is, maybe it isn't. But I think it's safe to assume you as a medical student (however old you actually are) do not have anywhere near the knowledge, experience, and more importantly wisdom to know how long is the right amount of time to live. A finite life is what makes special things special, and it's gives a sense of urgency to beings, not to mention it helps solve some of the population capacity's of the world. These are just a few of the many varied aspects one must consider. Perhaps God knew that one day we would learn how increase our well being. There is inherent wisdom gained by solving problems like how to increase one's life span vs just creating the ultimate long lasting creature. Is a miracle asking god to give you the lottery numbers? Or is a miracle giving a single mother the wisdom, strength, and love to raise 2 kids in the ghetto, keeping them out of trouble and becoming successful members of society out of no opportunity and poor circumstance.
Personally, I am not super religious in the absolute sense of the word, but I believe in God and the healthy benefit of believing in something greater than yourself. Personally I see science as a tool for religion. I agree that unfortunately it creates many close minded people. I also agree with a previous poster that it is good to question things. However, in an objective line of questioning, one should not only question if science disproves religion, but if it can also provide support for its pillars. It is very much a matter of interpretation and personal choice.