Girlfriend drove through big puddle and killed her 2003 Saturn ion I changed the spark plugs and drained the oil and transmission fluid is next because It’s revving consistently at 4000 RPMs I’m just checking to see if there’s anything else I missing before I start it up and drive it again

 

Did you remove the spark plugs and crank it over several times to expel any potential water from the cylinders? If not, you might try doing that and checking the plugs to see if there's any water on them. BUT, if it's constantly revving at 4000 rpm, it sounds like a hell of a large vacuum leak to me. Did you get all of the hoses connected back in the right places before starting? And did you check the air filter and air box for water before starting it?