Always disconnect the battery. I've welded on a lot of vehicles, though they are the last thing I want to weld on, bikes exempt of course, and have never had a problem with computers. But not being familiar with what makes them tick, I would check with an electrical guru first. It may be really easy to disconnect to be on the safe side. That being said, find the end of the crack, centerpunch it and drill it so that it doesn't continue later. Also make sure the welder connects the ground lead as close to the area as reasonable & never ground to a shift lever or any point whiich will carry a bearing. When current makes contact on the bearing surface, you'll have a hard spot and it will commence to pound the snot out of it. Let me know how you make out.