There are plenty of threads on here on how to do a proper engine cleaning just use the search button or use the autopia guide to detailing.
But for that new of a car, it should not be that dirty. Here are some helpful hints.
1. Have the owner sign a waiver he wants you to do the motor and that you take no responsibilty in case it will not start up. (I have heard from several reputable detailers, the owner of the car could already have a problem with the car, and than blame you for just cleaning it, you just never know, or you might even screw up the engine by getting water somewhere it shouldn't be also).
2. Put aluminum foil over the alternator and/or cover up electrical connections. Some people spray the connections with Wd-40 to insulate them from water. But cover the alternator.
3. If the engine is not too dirty (like yours probably), a good all purpose cleaner APC, should be able to get most of the grime off with a good brush, if you have a steamer that would also help. Lightly rinse the car off, but DO NOT CONtinuously soak the engine with water.
4. Coat the engine with some time of protectant, my favorite is 303 aerospace hands down, I have used tire dressing, Megs hyper dressing, and numerous other things. But so far the 303 looks damn nice and it adds protection to the hoses. Plus it doesn't smear or leave smudges like other products.
5. Also, if you have the time, use a paint cleaner to do the paint on the underside of the hood, it does make a difference when the paint shines on underside of the hood. You could use Megs Color X, Aio, Vanilla Moose, etc, whatever, just clean and protect the paint. Before that, you might use a APC to get the grime off in that area. Just use common sense in the engine, if you screw up and the engine doesn't start, you are in BIG TROUBLE.
Don't get water near spark plugs either, but on the new cars, it seems like everything is covered up.
This is the short version of it. Just be careful. It's not that difficult or time consuming unless the owner wants a concourse detail, but than he wouldn't be driving it.
Sounds like you got a nice car to detail.
Good luck, and do a search on detailing engines, you want to make sure you do it right on such a nice vehicle, (but you will like 303 especially for engines, it doesn't attract dust even over time)