Sorry, I was not fit for work during last 3 days and the pending tasks right now are web design resp graphical stuff anyway which I simply dunno how to do and hope for dos1 to get around doing it. I'd also appreciate any paid help by another professional web designer.
For the "import of, and account creation for, all our customer (payments)" I'm considering an approach where you actually create the account by yourself and then send a in-system-message to "management" to link clearly specified payments of yours to that account - we need to review each single one of the payments manually anyway.

cheers
jOERG