About 6hrs total flying time in a 152 in nil wind. It is capable of making its way up there with a runway eleveation of 6580ft. 528nm if you take the "direct" route. Very interesting ski-jump layout that lands into the mountain.
Altiport training required before a flight is accepted into it. There is a flight training school there that has a 172 and Jodel I think. They also have a C150.
They have 2 ratings, a snow free rating called mountain wheels rating. You can then do a snow extension. You can also do a specific altiport rating that covers you for use of that facility but needs to be maintained by 6 month flights.
http://www.adgs.com/C/GB/ecole-mtge-roues.htm
I hope this helps.