I went to the Silvretta last March. We flew to Munich and then took a train to Innsbruck . Was very straightforward, there is a station in the airport. Obviously if you can fly direct to Innsbruck even better. From there we caught a train to Landeck and then a bus to Ischgl. The bus is free for skiers. I don't know about Obergurgl but there is a train station in Oetztal from where I imagine you could get a bus. This is the site for transport in the Tirol http://www.vvt.at/page.cfm?vpath=index .
