The federal law on healthcare (KVG) can be foun here:
http://www.admin.ch/ch/d/sr/c832_10.html
The (main) ordinance (KVV) can be found here:
http://www.admin.ch/ch/d/sr/c832_102.html
The ordinance on coverage (KLV) can be found here:
http://www.admin.ch/ch/d/sr/c832_112_31.html
A good overview can be found on the website of the federal office:
http://www.bag.admin.ch/themen/krank...x.html?lang=de
As per pre-existing conditions: They don't matter for the
mandatory coverage. Every insurer that operates in the canton you live has to accept you (art. 4 KVG). The insurer is not even allowed to ask about pre-existing conditions (art. 6a KVV).