Also plan on replacing the knock sensor wire and knock sensor, the knock sensor wire gets brittle and any movement of it damages the wire. Dealer techs couldn't confirm that the knock sensor itself goes bad, but due to where it is located it is worth changing it as well. You will also want to buy new head bolts, studs, or non TTY(torque-to yeild) headbolts, do not reuse the ones in it, and insist on this if you have a shop other than the dealer do the work.

I would also send out the injectors to be cleaned/rebuilt, and have the heads checked.

Providing you don't find any damage other than the HG and a valve or 2, it should run you about $1k to do the work yourself, or if you have more $$ than time or figure about $2k at a shop