[Sapote]

Op, the fuel pump is dying, weak and cannot transfer fuel from left to right tank, causing out of fuel while gauge said 100km more.

 

[Sapote]

Would it be smart to change Left fuel level sensor as well?

No, nothing wrong with it.

 

[Sapote]

but there seems to be a Fuel level sensor on the left side of the tank as well? Should I replace it too while I'm at it?

Why? save your money and the landfill.