Ah ok. Is there any particular module one should be interested in or is it just something not to mess with?
There are a few different modules that can be used (you can only install one)
VGS-1 is a voice storage/voice guide module.
Great if you need that stuff, but a pain if you don't. If you use the recording function, you need to assign a button for it. The voice guide thing is just annoying, or at least that was my experience with it after a week or so. I disabled it and not even sure which radio it's in anymore.
There are also encryption modules, ANI, man-down, vibration, etc. but you shouldn't need that.
The TK-3180 is produced in two frequency splits. Make sure you know which one you are getting:
TK-3180 K and K3 models: 450-520MHz
TK-3180 K2 and K4 models: 400-470MHz.
They RF boards are different, so get the correct one. I think they can be tricked into a few MHz outside the design, but do not expect a 450-520MHz radio to go all the way down to 440. Unless you specifically need to run on the UHF-T band, no need to get the K or K3 models. Those might be the "cheaper" ones you are seeing.
There are a lot of battery options. I'm running about 350 NX-410's, which are the same chassis radio but NXDN/800MHz. We haven't had any issues with batteries, in fact I'm running several KNB-33L's with 2011 date codes. I can usually get two full 8 hour days out of one battery, but I'm not transmitting much. Kenwood brand batteries are expensive, so after market would be a good option. We've had good results with PowerProducts.
If you do buy a new radio, I'd recommend getting a new antenna since you don't know for sure what the previous owner did to it. Don't buy the cheap ones off e-Bay or Amazon, they are often mass produced in China and don't always resonate where the seller claims. Get a genuine Kenwood antenna. For amateur radio use, KRA-27M3 is the correct model. 400-450 whip.