Revenge takes Time and Trouble to Brew

What if Billy never sees the letter; after all, Sullivan was really careless leaving it lying about. Given his earlier efforts to keep it from view, he should have put it in his desk. Note, I wonder if the scriptwriter slipped up technically. The Departed is set in the 80's. CD's were very new then. Would a CD burner and copying facilities be that easy for Billy to get hold of?