RoyBA

I have two Lexus RX 300, yr 2000 and RX 350 yr 2013. I am writing about my RX 300, 3 owners that i am aware, i am the third, bought it used. I bought it used for about 9K. We have had now since 2009 with 210K for mileage. There have been problems and fixed them as they came, starter replacement, moon roof leak, heater vent motor, side light markers, Elk ran into side of car. The issue I am writing about is: My dog chewed through rear seat belts and i want to replace them. The cost would be about 1800 dollars. i bought the belts from a junk yard off a 2000 lexus that was just in an accident. The belts are fine. I am wondering if there are/is a manual (step by step) to replace the seat belts.