So - surgery! 
Actually, as long as you take great care, it’s not incredibly difficult.
Have a look through this thread where I gave some tips to someone else opening up their MP for similar (and successful!) surgery. There are better images that explain things since they were posted with hindsight and specifically to explain … rather than just logging my experience as it progressed.
The video I found, and linked to in that thread, was the one that I found the most useful.
Also, someone recently manage to damage one of the ribbon cables to the front sensors when disconnecting/reconnecting from/to the circuit board above the gimbal (inside the shell). Those ribbon cables are delicate. There’s little slack and over manipulation isn’t something they handle too well.
Most of the connectors have been secured with one type of gunk, or another.
Once the connectors are off, examine both parts very closely to ensure that they are totally free of gunk before attempting to reconnect.
Reconnecting the connectors needs to be done with the greatest of care - making sure they are perfectly lined up. (That sounds so simple, but not as easy as one might think whilst not over-manipulating the ribbon cables that have almost no slack! See my previous link for the consequences of really thinking everything was lined up perfectly! 
).
When they are perfectly aligned, gentle pressure with a bit of a wiggle, and you will feel them “click” into place.
Any time - shout if you need to know anything.