PLEASE HELP!!!
We are remodeling our Kitchen n bath as well as adding a room above the garage. The kitchen was demoed and while moving drain lines n all, the GC noticed that the copper pipes under ground (concrete slab) are corroded. He advised this is the right time to act if we want to. he has yet to give us a quote for what's the added expense for that.

The technique he is suggesting is, leave the current copper pipes underground UNUSED. Run a new line from the mains to the ceiling (maybe Attic he said) and then come down wherever through dry walls.
Since I have no clue about plumbing, the only question I had for him at that time was, will the water pressure be affected to first go up the attic (2 floors) from the main line and then come down? There must e lot many rational questions to ask which I am not sure of...

Husband and I are not very handy/knowledgeable about all this. Just worried if he is honestly concerned and warning us about the corrosion and possible issues in future or just trying to run new line to make his life easier. Very confused how to validate?

Please advise!