Yes you need to save all the "T" post you can. But it ain't going to be easy to get to the old post. I have pushed the front end loader in to the old post and hooked a chain to each one and pulled them up. With the roots grown up around the post you will never pull them with a post puller. It takes a front end loader and a hook up man dressed in a heavy coat to keep from getting scratched up.

The last time I re-did a fence I put up a hot wire about 100 feet inside the old one while I did the work. Then removed the temp one.

greet news about the rail road. Can you get them to build the new fence too?

Good luck.