Help!! Oil change and radio code problem with my mazda3 2007
 

Hey guys. Im new here and i just got my first car, a 2007 Mazda 3. So i went to the mechanic to service the car ( get an oil change) and we discovered that the knot under is blunt and it wouldnt come out. So he tried chiselling it out and still no luck. So the only other choice im left with is to go to a welder to solder metal to the knot and get it out. Now the only problem is theyll have to take my battery out and the guy that sold it to me says i might need to input a code to get the radio functional again which he doesnt have. I dont know too much about cars so i didnt think it was an issue until now.. Ive searched online for fixes incase i have to input a code but i cant seem to find one specific for my car. Can any guru in the house help please?

All the factory stereos I've seen in Mazda 3's since 2004 have no stereo security code.