The Palm T/X is a truly awesome device. As a PDA, it is still quite functional, even in 2021. However, most T/X devices, made in the mid-2000's, will likely need a battery replacement by now.
You'll need a very small screwdriver to open the T/X, and you'll need a soldering iron. The T/X battery doesn't just snap into place, you have to unsolder the old battery and re-solder in the new one. It's not complicated to do, just a little time-consuming. Check youtube videos, and take your time.
On stand-by, the battery can last for weeks! On continuous usage, it'll last a day, and recharging is very fast and easy with the same charger you would use for Treo devices.