since your using the latest version of txd workshop, you should be alright, but a new feature is kind of the down fall that has you running into these errors.
The ability to browse the gta3.img file within txd workshop. Its supposed to work for pc, but doesn't seem to like the xbox version....
so my advice is to extract the .txd file from the gta3.img file first using the IMG tool:
http://www.invisionplus.net/forums/index.p...mp;showtopic=68then use your version of txd workshop to open the texture file or use an older version like this one:
http://www.invisionplus.net/forums/index.p...p;showtopic=313also if you'd just like to get the firebird running this one is tested and should be good to go:
http://www.invisionplus.net/forums/index.p...p;showtopic=612sorry for the late reply, school is getting more crazy by the day and work is no better so my free time to work on my site has been limited.
hope this helps
EDIT:
as a sidenote, the order of files in the gta3.img file doesn't matter because the game loads models by filename, not order.