@mlb_fixit you are right, they are not complicated. What they do need is to pay close attention about the connections. Just by the voltage and amperage of most of these batteries, you should already have realized that they are wired in a basic series / parallel connection. I just rebuild one a week ago which was a 48V 20aH battery. All of this from common 18650 ***13S 4P*** batteries. Again, not knowing the specs of your battery, I can only speak about the one I just finished. Couple of things you want to do for now. First, we need the specs for the battery. Then we need to see it. Post some well-focused pictures of the battery etc. with your Question [guide|21499|Adding images to an existing question - iFixit Repair Guide|new_window=true] We'll probably ask you that a couple of times :-)
Next you want to have some basic tools, a couple of good sharp knifes, something like a box cuter or Exacto knife is perfect. Then you want to invest in a handheld battery spot welder. You can get those for about ~$35-$45 USD You will most likely also need some extra nickel strips. Once you have your battery apart, it'll be easier to determine the size of those.
The steps in general are ==>disassemble battery==>remove insulation/shrink wrap==> disconnect battery control board==> evaluate individual cells==>desolder cells==> replace cells==>reconnect wiring/nickel strips==> reconnect battery controller==>rewrap insulation/shrink wrap.
As with anything else, common sense is definitely required. Even those batteries can pack a punch and can cause a fire hazard.