Just a note to anyone reading these comments for tips and advice. Don't forget that each step above also has the ability to leave comments and they don't aggregate down here. So, I recommend going to each step and expanding the comments there too!

Warning. Do not put "drops" of isopropyl alcohol down here while trying to remove the battery. I made a couple of mistakes when taking this out that I thought destroyed my phone screen. Luckily, it recovered after a few days.

I put a "few drops" of IPA down and everything seemed fine at first, but within a few hours my screen started acting wonky, and eventually went out all together. Letting is sit powered off overnight, I got my screen back, but touch sensitivity was almost non existent. I can only assume that some IPA got down into the screen, but luckily evaporated.

My mistake was using only 90% IPA. But the 99.9% stuff.

Also, don't put "drops". If you need to use it, apply a small amount to the end of your spudger tool (I've also seen some people use a playing card which is a bit more absorbent as a spudger here).

In the end, everything worked, but there was a lot of stress!

I too want to stress just how sensitive the fingerprint sensor cable is. Be sure you are only lifting the back away a very small amount until you are able to disconnect the cable. I thought I was being careful and ended up still putting a small tear in the cable!

The good news is that a replacement sensor is well under $10 shipped. Also, I'm not sure why this guide recommends the use of the software tool.

It is not compatible with the 3XL (and I'm not sure it ever was). I had some reservations when I read this when I had to replace my sensor, but I found comments else where stating that nothing was needed. Sure enough, when I got my new sensor installed, it worked with no issues. I didn't need to calibrate, or reset my device. I just needed to set my fingerprints up again.

No recalibration of a new sensor is required on the 3XL. You can replace a broken sensor with a new one and it should be properly detected by the phone.

No software should be necessary, though you will likely have to setup fingerprints again. When the fingerprint sensor is broken, the phone software may not detect it and Android will not even give you the options to configure fingerprints. Once a working sensor is installed, it should provide the options again.

This guide is wrong when it describes a recalibration for the 3XL, it is likely that this was cut/pasted from another device.