Evaluating A Collection Need Some Hints Please

Ok I've been to numerous houses checking out the oddball album and even checking out an extraordinary collection, bought a few boxes but more often than not explained that age doesn't mean value and grandpas old stamp book is just sentimental.
Well tommorow I am going to look at a huge collection that I fear may be a hoard - However everything is cataloged and seperated into countries as well as scott numbers. That in itself says attention was given but we are talking 8 boxes somewhat larger than shoe boxes .
Also what would complete 6 vol scotts 1982, 1990 and 2008 be worth ? I know to sell them the shipping likely equates to more than the value but great reference material none the less.
I guess my problem is as mcuh as I know about US/CAN and a little bit of other stuff I would hate to overlook something special because I have no clue. There is apparently a full box of germany spanning old new and inbetween , alot of russia with complete year sets 1974-1996, Cuba sets from 1990-2010 and so on. The later is really what concerns me as having that modern material may be a heavy majority. But then again if all that modern stuff is MNH it could be a huge face value.