The Maintenance Manuals don't tell you everything. Also they never have every single part in the IPC.
I found that the IPC was used more by mechanics than the MM. The MM normally has only words but the IPC has those nice exploded views with all the parts shown in relation to each other.
Have you read an MEL, it's not always black and white and is open to interpretation?
If you use your interpretation for a MEL item, you had better hope it agrees with the Feds interpretation!