on the headstuds, if you look under the heads, if you see a crown bolt, its stock head bolds. if you see a nut on a stud, then its studded.
on parts, you will hear various answers, but really you just replace what is needed cause the repair parts add up. if you are doing a hg job then yeah replace the oil cooler and egr if you want one for emissions. better off just deleting the egr. if the truck runs fine, i would just leave it till it is showing signs early on that it will need to be repaired. i would for now get a scan gauge like a edge cs or cts to watch the two most important engine temp readings. engine oil temp and engine coolant temp. must be within 15* of each other. if its more than your oil cooler is plugged up or is almost plugged up. the other reading to watch is your ficm. needs to be within 47.5-48v.
if you want a oil cooler that wont clog up, there is a air to oil cooler available and one of the sponsors of the org has one. bulletproof diesel. but the price tag is 2k.