That's an even easier job, but I guess it depends on how bad the rails are. I think I bought a new set of cables for $15 at Home Depot and it took 15 minutes or so to put new ones in. If the pulley bar is bent then that's a problem I haven't worked on, but if it's just the cables needing to be replaced to fix the leveling then it's really easy.

Here's the youtube video I used.

https://www.youtube.com/watch?v=XzsQuFj5ygU