I bought a 2006 G35 Sedan A/T that threw a rod and a 2003 G35 Sedan A/T for dirt cheap that has a running motor. The motor has 182k miles on it and I plan to rebuild it. Seeing that I'm new to this particular engine I was looking for some input on problem areas and replacement parts.

I plan to strip it to the long block unless there's a compression issue, then it'll be the short block. The only things I've found through research is the valve cover leaks and that the oil gallery gasket can be a problem, but I can't remember if that was on the DE, HR, or Rev-Up.

Plans are:
Inspect/replace timing components
Inspect/replace water pump
Replace oil gallery gasket w/EPS Tuning or Syntheseal
Upgrade oil pump to rev-up variant (not sure if this is worth it for a stock motor)
Inspect bearings and clearances on crank, cams, valve lash
Inspect cylinder walls and pistons (bore scope or heads removed)
Valve Covers (I'm not sure what to do there)

It's late, so I've probably missed a few things. My other option is an import motor depending on what I figure the cost of rebuild to be..

 

Oil gallery gasket was mainly an issue with the HR and VHR engines, as they used paper gaskets . I have heard they can fail on DE's, but extremely rare. If you are rebuilding/refreshing the motor you may as well replace them since you'll be in there.
I would recommend you check oil pressure manually, that will tell you the engines health pretty quickly.
I used a harbor freight oil pressure gauge and a glowshift oil filter sandwhich plate. My 04 w/ 160k miles at the time had ~32psi at idle warmed up with Liqui Moly 5w-40; minimum is 14 psi (I think) per the FSM.
I would replace the 3 timing chain tensioners, main chain guides and water pump at minimum. I've heard the crank timing sprockets tend to wear quickly, so check that. I'd go OEM for these parts as most my mechanic friends/acquaintances have told me that aftermarket seem to crappy
Valve cover gaskets are a common leak, the outer gasket can be replaced, but FYI the gaskets for the spark plug tubes are molded into the covers
I've heard mixed reviews of importing used JDM engines. Yes, they can have lower mileage, but if the motor has sat in the humid climate of Japan for years, its a toss up if you ask me. If you import, go with a reputable importer that stand by their products. Ask for a compression test!