If it is a 1997 Cavalier, it is already OBD II. 1995 was the last year they had OBD I in the Cavalier and even then, it was only in certain models.
The 3400 and 3800 SC are the 2 most common v6 swaps for a Cavalier. grandamld9’s links are probably the best place to look. Go on there and search around–a few people have done step by step write ups on how to do the swap.