Also, you really dont reset it. Disconnecting the battery only clears the codes, but if the problem isnt fixed, it will still come back on. Not sure who told you 3 days, but they were idiots whoever told you that. But what problems are you having. Disconnecting the battery really doesnt do anything other than clear the codes. We at the dealership use the disconnect the battery on the newer cars. It was meant for the new stuff like 2006 & higher that use high speed LAN. It doesnt do anything for the older stuff. It was meant when you have a logic lock up in between 2 modules from the High Speed Lan data. So whatever you problem is, most likely disconnecting the battery isnt going to fix anything.
Next time, post what the problem your having. Check Engine Light On>? If so, whats the codes