So since no one would tell me I'm nuts, I tried my plan a little last weekend.
I took LR out at one end of my tank, into a bucket of saltwater. I started a siphon with wide bore tubing and sucked some of my gravel and it's companion detritus into another bucket. That water was brown! I tried to let that settle and siphon to another bucket but thru the blue filter material. What a bust! I still had brown water after the filter step. So I threw that water out and replaced with my aged water change saltwater. Then I put the rocks back and did my other maintenance chores for the week. Only got some of the gravel out , about 10%. Perhaps it is good to make this change slowly. Good thing about the siphon method is that it sucks the detritus with the gravel, thus saving the display water from becoming polluted. Bad thing is that it sucks so much water with it, that you have to only take a little each week, or risk changing too much water at one time.