Generally a 58cm frame should fit someone in the 5'10" to 6'3" category, depending on exact proportions. What size stem was originally on the bike? Typically, the bike should come with a 110mm or 120mm stem, you could potentially go up to about 140mm, beyond that would probably not be advisable.
Most seat posts are marked with a "Minimum insertion point" usually 2-3" above the bottom. It's possible the previous owner cut-off the post, so getting a new one might be needed.