Thank you all. This trip was partly inspired by some adds about a ten day photography workshop in Repkong, but the price was high. So I arranged myself a 16 day trip there and included also the amazing Buddhist institutes of Larung Gar and Yarchen Gar. Even though I had to go alone the price for car, driver and interpreter and hotels was couple of thousand euros less, food costs were 6€/day on average. In a shared car it would have been cheap! It is either very difficult or downright impossible to travel there using public transport (language, closures), even though it is legal in theory and no permits are needed like in the Tibetan Autonomous Region.
It seems that only a handful of westerners have ever visited the actual Yarchen Gar encampment, at least when doing a search for pictures from there most photos taken inside the institute seem to be mine. Even the interpreter had never been inside to compound, just looked at it from across there river. Two travel agencies said it is not possible to visit the place at all, and the one I used wanted to allocate all of 2 hours for the place saying there is nothing to see.
The place is so remote that it took 5 hours to drive from the nearest sizable town, and 5 days to cross 1000 km of bad roads back to Xining.