Caterpillar D7G serial # question..

Hi I cant seem to to dig up any info on this D7G Cat ser# 3GF00167 ... lookin for a year and any interesting tidbits about it...its ex military w an sblade n a cat winch. Its something I may purchase soon.

apperantly it was used in or near salt water as its got a lot of rust, which is another question...when should you realistically start to be concerned about corrosion?

Thanks all!