If your going through all that might as well install the chip internally
auto
Also try soldering the caps and charging them with a AA battery check them with multimeter. Could be a bad charging circuit rather than bad caps.
Easiest way to avoid updating is to just disable wifi. Since you can't play online with the DNS or access eshop, save some battery and risk and just disable wifi.
Its just a plain white screen. I have it working on my 2ds and I made sure the boot.nds is in the root of the sd card. It just stays at the white screen on my friends 3ds