as far as the washer, depending if everything in the inside is dry maybe take off the back and place a fan on the components, allowing them to dry for a few days, try it after say 3 days of the fan blowing on it.  If it is dry it may weel work.  I would take bleach to everything you can wood plastic concrete, even if you were to put it in a pump sprayer say dilute it 50/50 with water and spray the area liberally, that should kill the mold spores.  Wash everything that fits in the D/W with a lot of D/W detergent.  D/W detergent has chlorine in it, so it should almost sanitize everything.  Wear a mask, I would get a real painter's mask one that has the filters on it so u won't get any bad spores or fumes from the bleach in your lungs.  As far as the oil tank I would if it looks OK keep it if it has old oil maybe try to recover it if it's bad or just try to use it otherwise, it should be OK, remove the old pallets just because, they will become a fire hazard or attract bugs which you don't want anyway.  the shelving should do OK with bleach spray and wipe.  Be very careful as well using goggles & the air mask when you mix the bleach and water.  Taking your time is probably the best way to do this, then figure out why you had 6-8 inches of standing water and fix that problem either with a sump pump or something.  Good Luck