The real answer is:
Some parts have to be replaced every 2200 hrs or 12 years (whichever comes first.)
A few parts (tail cone, ?Tail rotor gearbox I think) Skid cross tubes - get 2 cycles (4400 hours) before replacement.
Some parts have no limit on their life.
If parts have been replaced along the way they don't have to be replaced againat the overhaul until their time is up. You don't have to replace with new parts, you can replace with used provided you have all the history and paperwork with the parts and they still have life on them).
My experience when I had mine rebuilt was the total cost of a rebuild was somewhere between 1/3 and a 1/2 of the price of a new one. But a bit hard to actually put a price on it as when we pay for our parts depends on the rate of currency exchange at the time.