How would I rename light bar textures? For example emerglights.png to emergfed.png and emerglight_ems.png to emergfed_ems.png

(Trying to model an ambulance)

Just.. Rename the files like you normally would?..

How would I rename light bar textures? For example emerglights.png to emergfed.png and emerglight_ems.png to emergfed_ems.png

(Trying to model an ambulance)

I'm not 100% sure if it's the case with GTA 4, considering everything is all in a .wtd file, but you'll need to have access to the unlocked model to change the name of lightbar textures. This is because when you UV map something, you have to tell the model what file it should use as a texture for that mapping. That file will have a specific name, and if you change that name without telling the model, then it won't be able to find the texture it's supposed to use, so will appear untextured in game.

The only way to do it is in Zmodeler with the model itself, you can't do it with models that are locked though as those textures are assigned to materials by that name permanently. Go into the texture browser and select the texture you wish to change the name of, then click on the replace button and navigate to the file with the appropriate name to your liking.

Yes I have a lot of unlocked lightbar. Is there a tutorial?

The only way to do it is in Zmodeler with the model itself, you can't do it with models that are locked though as those textures are assigned to materials by that name permanently. Go into the texture browser and select the texture you wish to change the name of, then click on the replace button and navigate to the file with the appropriate name to your liking.