Well after you've added the rows, changed the texture references in those rows and hex edited the model to your new custom texture, you have to edit the actual UTC file the Mandalorian NPC and change its appearance to your newly added row. It can be found in KotOR tool through this path (if you're using the Mandalorian Camp on Dxun)
KotOR II -> Rims -> Modules -> 403DXN_s.rim -> Blueprint, Character
However, more than likely many of the Mandalorians use the same UTC files, so, if they do, you'll have to edit the UTC to have a custom tag/resref and edit the module's GIT to make every single Mandalorian unique.
By the way, if you're ever looking to do more modding these lists of modules and their corresponding identifiers is quite helpful:
KotOR 1
KotOR 2