When I run into problems with any of the Sierra games I consult with the expert… Tawmis. He runs a set of webpages and has written scads of patches, updates and general hint tips to make playing on modern computers possible.
If you can’t find what you need there, swing back by here or over at Sierra Forums and I’ll try to help you out. I check “my” area of the forums (SierraVault) once every few days, here a little less.
Good luck. Kings Quest 8 was a great game. I’ll probably get run out of the Sierra community for saying so but I enjoyed it, warts and all.