Recently (January 31 more or less) I installed luma 3ds in my 2ds and wanted to be prepared to not have any unexpected problem, should I do something before installing the update?
yep
Make a NAND backup and then update normally. If you use 3dsx based homebrew you will also need to update both the HBL cia and the homebrew menu boot.3dsx. You may also need to use Luma hourly versions instead of 6.6. Also, be sure to update NTR Boot Selector if you use NTR.
ALWAYS make a NAND backup before a system update or any other major change.
I would recommend you download this software: https://gbatemp.net/threads/release-homebr3w-simple-homebrew-browser-and-installer.434105/Where I get the updates of the homebrew launcher and the ntr boot (new in this type of thing)