If there were extraterrestrial life, it would not affect my faith because it would just mean that God created them too. But even if extraterrestrials existed, it would be impossible for them to reach us. Space is so vast that even traveling at the speed of light, which is an impossibility according to physics, it would take hundreds of thousands to millions of years to reach us depending on their location. Even if they had the hypothetical technologies to create wormholes or whatever to bend time and space and travel instantly, there is still the question of how they would find our planet in the first place. There are an estimated 200 billion trillion stars in the observable universe. Finding Earth would be like finding one specific grain of sand in the Sahara Desert, a virtual impossibility. How would they even know there is complex life on earth anyway? We've only been broadcasting radio signals into space for 120 years or so. Radio waves also take time to travel through space and degrade over distance.
Having said that, it's possible we could get an alien visit. And by aliens I don't mean extraterrestrial but rather extradimensional. In general, all angelic or supernatural entities could be classified as extradimensional beings. They could also be classified as "aliens" as they are non-human entities. The Bible describes several such classifications, including seraphim and cherubim. So, clearly, there are other beings out there that God created besides humans. Some of which we know about and others that we may not.
One particular entity of interest that the Bible does mention is the Watchers (Dan 4). Those Watchers were loyal to Yahweh (God), but there are other Watchers who rebelled against Yahweh. Depending on your take on the Book of Enoch, it describes an incursion of 200 rebel Watchers who descended to earth and corrupted humanity. The things it describes certainly sound like genetic engineering on both humans and animals, which ultimately led to the Great Flood in Genesis. To the ancient world, the Watchers may have seemed like gods. From our modern perspective, we would think of them as aliens. But really, they are an angelic order of beings who rebelled against God, violated their decree, and were judged severely for it.
I'm sure I will knock over a few sacred cows by saying this, but it may be that we need to revise our concept of what angels are and look like. We think of them as ethereal beings clothed in white, and the Bible does describe some that way. But there are different classifications of angels, and they're not all alike. Some, in fact, may be more corporeal than we imagine, like the angels that visited Abraham and Lot (Gen 18-19). They could be seen and touched and even sat down and ate a meal. It's also conceivable that they possess some form of technology that is "alien" to us.
The Watchers in Enoch are currently bound and awaiting judgment, but there's no reason to believe that there are not other rebellious Watchers out there, attempting to illegally trespass on earth. Ecclesiastes 1:9 says, "What has been will be again, what has been done will be done again; there is nothing new under the sun." I believe this also could set the stage for certain end-time events prior to Jesus' return and the great deception that is talked about in 2 Thessalonians 2:3-12. No doubt if they suddenly showed up, it would cause many to fall away from the faith and be deceived.