I have some replacement parts  and backups for my rifle. However I realize that If I needed to replace certain parts of the rifle, I wouldn't know how to perform these repairs.  Is there a field manual or repair and replacement book that you could recommend?  I would love to familiarize myself with certain aspects of potential repairs and have this book handy.  Thanks in advance for your suggestions.

Free pdf download
https://tiwazarmament.com/ar-15-m16-m4-service-manual/

Gunsmithing the AR-15, The Bench Manual Vol. 1, 2, and 3: By Patrick Sweeny
Apx. $30 per volume. Very handy hard copies to have with great pictures available at amazon, Midway, etc

exactly what I’m looking for. thanks for the recommendation.

Here is a Colt one https://www.coltcanada.com/wp-content/uploads/2021/04/10044s-2005-09-20.pdf