What tool/s and materials do I need

Hi,

Here’s a link to the ifixit iPad Pro 12.9" Teardown guide which shows the tools required to completely dis-assemble the tablet so that access to the rear cover is possible.

Here’s a link to the ifixit iPad Pro display assembly replacement guide which shows the additional tools (not mentioned in the above link) and the parts which are required when repairing an iPad Pro.

Hopefully the two guides will be of some help.

Unfortunately ifixit does not stock the back cover in its’ list of replacement parts for the iPad Pro12.9” 1st gen. You will have to search for other suppliers of this part. Just search for iPad Pro 12.9” 1st gen. back cover part to get results