Seems like a tight fit getting to the back of the gauge cluster.
it is even for me and im slightly wider than a 16 penny nail. as for the wrench, what ever fits. patience is the key here. lay on the floor of the cab and weasel your way up there with a good light and take a look to see whats up and address it. it would help if you had a helper to get you what you need to minimize how much weaseling you have to do once your in position.
another way is to pull the speedo cable and remove the speedo and then you have a hole to see through with limited access.
