Welcome to the forum. I'll try to answer some questions, and others will chime in too. This place is a good resource.
The phone will work, but it requires some nursing these days because of lack of support from HP. Work-arounds are all available and described in this forum. One primary issue is lack of Palm Profile support. You have to use the phone in developer mode. This has no consequence other than lack of a cloud backup. Hopefully your friend was using the phone recently and is aware of the adaptations we've all made this year. If not, you have a lot of reading to do. But it is described here. Focus on threads by PREEMPTIVE and look for articles by PIVOT CE. They are the best resource for catching up!
As far as power goes, batteries online are hit or miss. I just wrote a new thread describing my experience. Good luck shopping. At least they are cheap.
The TS is very handy once you become used to it. But if you are OK with doing what everyone else does, just keep plugging it in until you feel compelled to pursue it. The TS requires an OEM cable and charger cylinder to work, so you'd have to get one.
If you decide to get one, it sort of helps turn your phone into a desk clock. The screen does stay lit so you can read the time, but pressing the power button will make it black out so you can sleep in the dark no problem. You can also assign a few apps to work in the desktop "exhibition" mode. But it's really just a convenience of not having to plug in. Once you get used to it, you'll always want it so be warned. Mine (1 of many) is mounted to my bedpost so yes, i do wake up every day and think I'm glad i have it! Haha
These days, the best source of replacement parts is other used devices. So if you need a digitizer, you'd buy another phone and swap the screen. Parts interchange easily among models and carrier versions, and that is discussed here too.
One other thing is the "Doctors". The software to flash the phone was readily available from them MFG once, but is harder to find now. But there are sources described here. When you doctor it, you reflash. This can help fix issues, but then you're beginning the path of reactivating without a profile. You'll follow steps described here for "bypassing activation" screen.
It's a fun device, still mostly functional. I use it every day and love it. Become familiar with Preware as that is our source for software downloads now.
Good luck and welcome to webOS!