Help at the Post Office (München, DE)

Hello there. I am managing a project of one of our clients (we are an Advertising Agency). The task is to handle sending of a traditional paper mailing campaign (printed, in envelopes). I need help from someone local from München to assist me and translate everything at the Post Office, basically get the job done. I will have around 6000 letters to post, each at the rate of 0,70 EUR. I'm offering up to 100 EUR for your help, shouldn't take more than a couple of hours. I will personally be there with the letters (but my German is very limited). In order to prepare for this task please find out if we will need anything in particular before we can post this amount of letters. Perhaps it will be necessary to go to several post offices instead of just one?