Theo schrieb:
of course i *would* like to use book(koma-script). But i don't know 1) how to change the headline font to serif (just something normal, not that fancy)
That's easy, use the command similar to \setkomafont{captionlabel}{\bfseries} For the exact command have a look at the koma-skript manual: http://www.tug.org/tex-archive/macros/latex/contrib/koma-script/scrguien.pdf
2) how to tell lyx to start numbering everything with 1 - and not with 0.1
What do you mean? The section numbering in koma-book starts with 0.1 when you don't have a chapter at the start of the document. You can easily switch from the xxx.yyy numbering to another one, have a look at koma-scripts manual.
Koma-scripts offers you many things you normally need extra packages for, e.g. the caption handling, title page and TOC formatting, and of course its famous print space calculation (no need to set the page border manually and binding correction is supported).
regards Uwe