HUD mods do not need Lua scripts (at least at the basic level, that is, graphic replacement).
All graphics in SRB2 are located in
srb2.pk3
, so all you have to do is just make a separate mod and add graphics to it, making sure that the graphics you add are named exactly like the graphic you want to replace.
And optionally, if you want to move these HUD elements, you can
use a SOC configuration file to do so.
That's pretty much it.
You can open
srb2.pk3
with SLADE (recommended) or any zip explorer.
If you want to do something more complex than just graphic replacements or moving HUD elements around, you
will need Lua and there is no way around it.