Make engine wash yourself or rather by the expert

Hello, I’ve been looking into the engine room for some time now and found (almost terrified) that the interior is pretty dirty. So I want to give the car an engine wash, because that’s not how it works (according to the motto: outside hui, inside pui)… Can you do something like this yourself? If so, what do you care, what do not do, etc.? Or rather let the professional do it? BoisBleu