Are there any concerns in regards to cleaning the engine with aerosol cleaner and high pressure water? Areas to avoid for fear of causing more problems than leaving it dirty?

Electrical connections. Mainly the PCM and ECM stuff. You don't want to short anything so yeah. Most things are water tight but high pressure directly on them could penetrate the seals. Put the spray jet on the wide fan setting for electrical stuff and just give it a quick once over.

I typically use Zep Orange degreaser and my garden hose with a spray gun. I normally let the degreaser sit for about 30 minutes or so and then rinse with the garden hose. The only thing I've seen problems with is the WIF light popping on to a wet connection. Normally I would blow out the connection with compressed air and then add some new di-electric grease.