To replace the sender unit you have to drop the tank.
But just to let you know, it is a pain in the A..
I had to replace my fuel pump so I know.
But it is doable.
First you have to drive until you tank is almost empty to get rid of the weight.
Then you need to disconnect the battery and release the fuel pressure on the fuel pressure valve (see picture).
Next thing you need to do is to release the fuel tank pressure by removing the gas cap.
Then disconnect the supply line to the tank and also the vent tube (sorry I got no picture of that).
But check the link and you will see what I am talking about.
Ok, now support the tank with a floor jack and remove the nuts which hold the skid plate and the tank (see picture).
BUT do not remove the one with the rubber cap.
These two secure the tank to the skid plate.
If you done that then you can slowly lower your tank.
But you will soon notice that there is not enough space to just lower the tank.
So you will have to work your way trough and around the frame, rear spring, and exhaust pipe.
When you done that, than you can disconnect the fuel supply lines which run to the gas pump (see picture).
Now your tank should be right in front of you !!!
Next thing you do is to remove the nine bolts which secure the fuel pump to the tank (see picture).
Once you done that, just pull the fuel pump out of the tank and you will see the sender unit, it is the big black rectangle (you can see that in on of the pictures as well).
Now you can replace the sender unit.
On other thing, while you got the tank out.
If you don't know how old your fuel pump and fuel filter is, now is a good time to replace it.
And you may want to wash the tank out as well.
If you reinsert the fuel pump into the tank don't forget to use a new seal which is a $1 at your local parts dealer.