Two simple scripts to work with Monkey Island Special Edition pak files
extractpak -- extracts all files or one from the pak file. 2nd argument is single-file.
./extractpak Monkey1.pak art/rooms/images/89_cu-works/layer0_chunk_0_0.dxt
dxt's are saved as dds', too, edit those, then make sure all layers are merged and resized to the image size. If the image has any transparency, export with dxt5, otherwise with dxt1. Backup Monkey1.pak, the next command replaces the files in-place.
./packpak Monkey1.pak art/rooms/images/89_cu-works/layer0_chunk_0_0.dds