1) Yes, actually LAN is the preferred and commonly used connection

I've never seen anybody using that modem port.
2) I guess any satellite, if you have a proper LNB and there is DVB-S or DVB-S2 broadcasted.
3) Depends on your demands. First of all you should flash an up-to-date image (how-to:
http://www.dream-multimedia-tv.de/en/dm8…irmware-browser). The official images are provided here:
http://dreamboxupdate.com/opendreambox/1.6/dm800se/images/
For recording, an internal 2,5" SATA or an external eSATA disk would be fine. But recording on a server or NAS does it quite good too. If you wanna play around a bit, a USB flash drive is a nice gadget (for backup purposes, picons, etc.). Just read around this board and try google, there is enough reading stuff, also in English