New pipes question

There is not enough information here for anyone to give you an informed decision. If water is flowing out of your fixtures without a problem, just let it be. Repiping a house can cost thousands. If you don't know what to look for as a homeowner, many thousands of dollars. If you decide that's the route you want to go, get multiple bids in writing.

We typically abandon the old galvanized pipe in the walls and run everything with pex pipe because it's flexible enough to maneuver through the walls. Material for this is fairly cheap. It's the labor that is going to cost you. I typically would block out 2 days and 2 guys for a job like this.