Next week hopefully BI will be releasing their newest version of Texview.
When they do, get it and install it, it will allow you to view ArmA .paa files.
Once you have that, dePBO the PBO that contains the model you wish to retexture, I recommend using Mikeros Eliteness to do this.
Eliteness can be found in many places, there is a version in the Editors Depot on this site, a link is at the top of this page.
For example, if it is a soldier unit you wish to retexture it will probably be in the characters.pbo.
From this folder find the model file you wish to retexture and load it into a hex-editor, the Cygnus free edition I mentioned earlier in this topic will do fine.
Search with the search function in this editor, search using .paa as the search criteria, make a list of all the .paa files you find and their paths.
The .rvmat files are also listed there, but I would leave them as they are for now unless you want to change them and know what you are doing.
Next go to the folder containing the depbo'ed characters.pbo and find these textures, load each one into Texview and note the dimensions of each texture from the model you wish to change.
Texture dimensions must be in powers of 2 (2, 4, 8, 16, 32, 64, 128, 256, 512, 1024, 2048).
Texview will tell you what each texture dimension is.
It is best that the texture you wish to use is of the same dimension and quality as the original texture.
The texture you wish to use should also include an alpha channel if the original texture also uses one, any alpha channel can also be viewed with Texview whilst viewing the original texture.
Once you have all the relevant information about all textures used by the model you can then load the model back into the hex editor and change the textures and their pathways to reflect the textures you want to use.
A word about the texture names and pathways from the original model file:
If for example the pathway and texture name was... ca\characters\data\camelpilothhl_dt.paa ...as an example.....then the new pathway and texture name must be exactly the same length in characters.
With MLOD files this is not so, but with ODOL files, which is what you will be working with it is important.
MLOD are un-binarized model files, but ODOL are binarized.
I hope this has been helpful to you.