I looked and could not find the two matching blocks!. I have made similar "mistakes" and always choose not to rip it out. You spend so much time staring at your pieces from 8 inches away, you will notice so many things that nobody else will!
Regarding the light colored block. Firstly, I am impressed that you identified the issue. I didn't understand the importance of value and contrast until years into my quilting life. That being said, don't rip it out (the cross is still noticeable from a distance), and congratulate yourself on being ahead of the curve. Use this insight to make an even more awesome 2nd quilt!
overall, though, I recommend just stepping back from the quilt, maybe even stepping away from it for a while. Ripping can be very aggravating and depressing, I would not want you to invite that into your first quilt! Enjoy the process. DO NOT point out these "mistakes" to your friend, and simply bask in the glorious response you receive from him/her when he/she receives your wonderful gift!
Welcome to quilting. Welcome to the board. We have very friendly and knowledgeable folks here, so don't be a stranger!