In reply to jbpilon:
Suilven has some steep ground to gain the ridge, but from the col to the summit is easier. I would expect the steep section to be snow covered, since the general snow line is around 400m, but it is probably low enough to be reasonably well consolidated - of course you should use your own judgement on the ground.
SAIS reports and blogs are probably the most reliable sources on online conditions info fro the area. You might get lucky and get a relevant report on the UK Ground Conditions Facebook page: https://www.facebook.com/groups/345833125602252/
You should probably moderate your ambitions with respect to An Teallach: just going as far as the top of Sail Liath would be rewarding in terms of views on a nice day. It is possible to gain both Munro summits from Shenavall via Coire a' Ghamhna, but this could be hard work and/or avalanche prone. River crossings permitting, Beinn Dearg Mor would be a good objective from Shenavall - it looks spectacular, but there is a a fairly straightforward route up its SE corrie.