I'm flying UA IAD-MUC then transferring to LH MUC-GRZ. I have about a 4 1/2 hour layover. My first time through MUC so I've got a few questions:

If I just transfer (i.e. don't go airside), would I go through security again in MUC? If I buy some duty free liquor at IAD, can I get it all the way through to GRZ carrying it with me? Or would I have to check it in MUC? Are bags picked up and then rechecked there as well? I will have UA check mine all the way to GRZ.

Will the shops at MUC be open on Christmas Day?

Where are the showers located (not the lounge ones)? Are they airside? Anyone know the cost? Think I read there are vending machines with soap and towels.

Thanks a lot.