If you want it new again it may be a bit late, I have cedar also. My
friend tried all the commercial cleaners out and found Sherwin Williams
the best. Mold is its own issue, the straight laundry bleach in a garden
sprayer will kill, it also cleans somewhat. I would go learn about
Sherwin Williams product, it is im sure 10-15x the price of bleach but
might be worth testing a sample area comparing to straight cheap laundry
bleach. Don`t dilute the bleach, it already is 97-98% water. On coating
it depends on your cleaning results and the look you want. Read Consumer
Reports ongoing 8yr? stains testing. If it comes real clean a clear or
transparent product will look best. Mid ground Semi transparent. if its
blackened its aged to far and solid color is needed. With 3 years and a
good clean if it restores itself a clear or clear with slight tint would
look great. Mine is real old and black I had to go solid. Try to pick
the longest lasting product since they only last a few years. Im pretty
sure Consumer Reports has Olympic clear at the top. You will need a
power washer. Buying a cheap electric 1300 lb will do, but get a good
brand. I went through 18 gallons last fall of bleach on a small moldy
house. Im sure the Sherwins product is Sodiun Hypochlorate [ Bleach} and
an acid or alkaline cleaner combo.