upgrade to a blue 15A fuse. Its a common problem when the pumps are changed out.
as for the oil pressure gauge, that problem is also somewhat common, just happened to me last june driving out to Nats.
To fix it, you have to remove the gauge cluster from the dash and remove the plastic guard from the cluster. Then carefully pry the needle up over the top pin (do not break the needle), rotate it clockwise back around to the bottom pin, lift it over the bottom pin and leave it.
put everything back together.
next time the truck is started, it should be back to normal.