Hi Shelagh,
Long time, no speak. Hope you're well, and glad to hear you're still running.
We keep talking about going to Poland, and it will happen sometime. I've also looked into doing races in Poland. The Warsaw marathon is in September usually, with Kracow in April.
Essen/Munchen I don't know anything about, I'm afraid. I suppose you've tried
http://www.marathonguide.com? They have a lot of race reviews from runners. The other suggestion is that you visit the British Runner's World forum -
http://www.runnersworld.co.uk/forum and do a search for Essen and Munchen/Munich. There are a few Germany-based runners that use the forums over there, so you may well find something. If they are anything like Hamburg, they'll be well organised events on well-designed courses.
As for transport, depends how much time you have. If I had the time, I would hire a car and meander across Northern Europe - there's a huge amount of interesting stuff to see. If time is a bit tighter, you'll find the train service fast and very efficient. At Hamburg Station you could buy train tickets for destinations all over Europe. It would also give you the chance to see the countryside.
Do let us know how it goes.
Andy