98 Nissan Altima Heater Blower Stuck on High

Good day to you!
I have been having difficulties with my 98 Altima for a while now and her latest issue is that the first three levels of the a/c and heater fan don't work even though the final, fourth, level works fine. I've done my research and I think I know what's wrong. It's that the resistor box for the blower has burned out. That resistor box is supposed to be under the dash on the passenger side.

Now, before I start unplugging the battery and unscrewing stuff down there, I would appreciate some confirmation that I am doing the right thing. Do I really have to unplug the battery? And if so, which side is more important? Do I even have to remove the dash or can I fix this some other way? Please know that I have little to no experience in car repair, aside from some recent battery issues. I still chose to attempt this myself after reading a number of comments about how easy it was to accomplish.

I appreciate however much time and help you would give me. Thank you.
You may not need to disconnect battery. Always suggested if you do is to remove neg side and the reason is if your tools hit the body of the car they don't cause a problem.

It probably is the resistor and for many cars they are on top of the distribution box,