New Plugin - how get transponder info of current service

Hi guys

I'm writing a  new plugin.

1.how can i get transponder info of current service(tv channel) like freq, symrate,Pol,pids(SID,PMTPID,ECMPID)  and save this as string data. I don't want this info for skin.

2.which module files should be imported? like this :

from enigma import iServiceInformation, eTimer, eDVBFrontendParametersSatellite

3. how can i find all properties of a module like  iServiceInformation or others?. I just find PluginDescriptor in /usr/lib/enigma2/python/Plugins/Plugin.py

thanks a lot