I just repaired my sensors as well. It is VERY difficult if you don't have the correct tools. But anyway I bought CH-48482 (for GM) which is much cheaper($18) than J 46211 ($100) and managed to hammer it to fit murano lock ring. (CH 48482 is about 0.5 cm smaller from tooth to tooth).
Working on the passenger side is MUCH easier so I recommend that you start from it. If the problem goes away after the passenger side is done you are in good luck.
In my case I did NOT replace either sensor (potentiometer) because as I an electric engineering major I believe it should almost never fail given the working condition and current applied on it. The contact track does need to be thoroughly cleaned. Once done it should be as good as a new one.
The design of murano fuel sensors is a series of two sensors so if the fuel level is lower on side and high on the other as a result of turning while driving, the combined resistance is compensated and should be relatively stable, reflecting the average fuel level of both sides of the tank. After cleaning both sensors you may want to use a multimeter to test the series resistance to make sure connection and sensors are both in working order.
A caveat before you snap the floater piece back to the sensor: you may want to bent the two contacting points slightly outward to make sure they apply some pressure on the potentiometer track. A problem I encountered was that when the assembly was outside the tank the resistance of the sensor loop was normal (around 89 ohms depending on how much fuel you have in the tank). But once I put the assembly back the loop became open. Finally I found as the contacting points on the floater swing back to the middle of the track the pressure was too small to make a contact and the loop is discounted.
Another warning is that putting the lock ring back on the driver side is EXTREMELY difficult because:
1. The assembly has springs that push the bottom of the tank so you have to offset the pressure in order to press the ring as low as possible to the floor. I think the new seal is barely adding much additional pressure because it is relatively thinner than the displacement of the spring.
2. In order to lock the ring you will have to simultaneously push ALL five points on the ring and turn the wrench. So you'd have to apply downward pressure and turning at the same time.
If you struggle with the ring, a way to temporary close it is to use five quarters (yes I mean coins) to lock the assembly without the ring. It is a lot easier but make sure you don't accidentally drop some of them into the tank adding to the cost of repair
I also made the work slightly easier by using dremel tools to grind a small ramp on each of the 5 openings on the ring where sliding begins. You may also use some small metal inserts to lock the ring down (one at a time) to the hooks before you start turning the wrench. This allows you to focus on turning rather than pushing and turn.
Good luck!