and fluid leaks which can be minor or major (as in engine removal) to fix,

ya prob don wanna deal with a rear main seal, or even the upper oil pan,

which is prob all original,

if the oil cooler lines are original and even if not leaking now, i'd replace unless perhaps there was some record of when last done,

when dealing with oil cooler lines, it is all too easy to wreck the oil cooler threads