Mono, you may want to ask the gunsmith to clarify that statement for you. Seems like a silly statement to make. Either the rifle is functional or not. If he was a authorized Remington gunsmith it should be properly fixed and you should have no problems with it.
It didn't seem like a silly statement to me. The 742's do wear out, and when the receiver is shot, it can't be fixed...at least not easily or at Remington.
I have an old 742, it shoots really good and is totally reliable, it's put a LOT of meat in my freezer. I don't target practise with it because i don't want to wear it out. For hunting use, it will more than likely last a couple more lifetimes..
I'd shoot that 742 to make sure it's sighted in with the ammo you use, and if it works well, take it hunting and don't worry about it..