im used AG engine bay cleaner and a power washer, just make sure all electricals and air filter (if not standard) is covered ie plastic bag.
spray on - rinse off, spray on, aggitate with brush, rinse off, all with engine on, done it several times, never had any problems.
As for cleaning your car, ive put a big how to in cleaning bit - do it yaself, worth it in end - unless you want paint correction with a rotary, then get a pro to do it as you can burn paintwork if you dont know what ya doing, then its a respray job lol.