i've collected since I was a child (now 66) and in my family I'm the last one standing and I have received more stamps. I have several boxes where (in some, not all cases) stamps were placed into glassine envelopes and somewher along the way there was enough humidity stick stamps with hinges together and MNH stamps to everything they touched...so I have some "chunks of stamps.
Would steaming be the best way to try and get these apart with the least amount of damage?
That is very unfortunate. I hope there were no higher value material and just more common. Did you try gently bending them to see if they will part? Steaming,or use of a sweat box, will take time but best if it is worthwhile material. Otherwise just plain soaking as like doing with used. No matter how you do it you will probably end up with stamps with very little or disturbed gum remaining. Basically used stamps. Good luck.