That previous owner must be a bit of a careless plonker. It only takes a small amount of time and effort to remove stickers carefully with a hair drier.
Steam from a kettle may help with checking the effectiveness of the conductive paint repair.
It depends on the type of hood/ screen you have. The glass rear window in my new hood is permanently fixed, unlike my previous one which had a zip in rear plastic window.
The process to swap a zip type plastic window involves drilling out rivets along the bottom bow and replacing them when fitting the new window section. That process should be just the same for a glass zip in screen section. Its not difficult, you will just need a drill and some small rivets. Allow a couple of hours if that.