Basement bracing and expansion joint questions

I bought an older house which has two of the basement walls supported by pony walls, and all four walls with steel braces. I was told that these braces need some "backblocking". Is this very essential and what would the approximate cost be for about 20 braces?

Also, I was told that the main stack may need an "expansion joint" to be installed by a plumber. Is this very essential and what may be the approximate cost?