Rog the route won't be on viamichelin, because they are more concerned with roads. I've been there a few times and the GR7 is quite well marked on the ground as it is to anadalucia as the GR10 is in the Pyrenees. Nice part of the world. The Sierra de Grazelema is beautiful, but be careful about wild camping and check out permits. as in the US certain parts of the National Parks there require a permit to enter.
Good advice David. I've lived here for a while and last week I was up in the central pyrenees. Crampons not needed, but there was still a lot of snow on the ground from 2300m upwards, it was also snowing and I was glad to be wearing a solid pair of boots. The cloud came down and it took me over an hour to walk the last km (I was on my own) to get to a refuge.
The editorial alpina map is quite good but lacks topographic détails. I used the 2008 edition and there are quite a few errors. A better map at 1:25 000 is the Adrados editions which can be purchased in the shops in Potes, Cangas de Onis etc. I was last there 3 yrs ago and a local guide told me it was the best map for the Picos.