Hi there,
As a German, I go back there twice a year to visit my family and old friends. I fly into Munich and leave from Frankfurt, renting a car in between.
Coins are in 1,2,5,10,20 and 50 cts, 1 Euro and 2 Euros. Needed for subways, parking meters etc. Bills are in 5,10,20,50,100 and 500. I never had a thousand, although they might exist. You can exchange at the airport or at any bank. I use an extra wallet for Euros and put the Dollars away at the airport.
The bills are more colorful and easier to recognize than all the “green”backs.
Munich airport is the easiest, Frankfurt has two terminals and a skytrain in between. It is important to know which terminal your airline is at, otherwise you are in for a long walk. Luggage carts are free at the airports.
Children start learning english now in 4th grade, but my niece and nephew at 16 and 14 don’t impress me with their english when they speak to my wife. But overall your chances are probably better with the younger folks 20 to 40. Larger hotels and restaurants will have somebody who will speak english as in most “tourist” areas. Restaurants often have english menus.
Autobahn signs are good, street names are often very small at the intersections. GPS would probably make sense if you travel a lot to “new to you” destinations.
Many years ago, I travelled 2 weeks through France without speaking French and I survived it, although I ate a few things that I might not have eaten, had I known what it was when I ordered it. I think it is a lot easier now to travel in Europe and the lack of language should not stop you from going. Enjoy it.

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Reinhard Kreutzer
1987 420 SEL (126)