LD20 Petroleum Motor with 90 Caled Chain

Hello everyone, I am writing from Chile, the mechanic stuck the condor of the year, opened the engine and the marks were lost and the chain of a Nissan LD 20 oil year 1990 can not be peel, part of 1990, part without problems but has no strength. Try to download the manual but it is impossible if someone has it please send it to , I don't want to lose my vehicle my jewel, thanks or if someone has it in Spanish version much better, thanks in advance
Benjamin

Good Benjamin, this is what I found of the LD20, I hope it serves you, greetings.