Centuries are not that hard provided that you are in the proper shape.
Since you seem to have no difficulty doing a metric, doing the next 37 miles for the century should be within your capabilities.
For a first century, there is good advice up there.
I would suggest:
No new gear or new adjustments. Go with what you got. Finding out that something chaffs at the 60 mile point is not good.
Stop relatively often and BRIEFLY. Eat a light snack, drink water, relieve yourself and let the blood circulate to your contact points.
I would also suggest that you ride at a reasonably sedate pace. Riding fast will deplete your glycogen pretty fast. If you ride slower, you can even finish a century without depletion. If you are feeling strong, you can always push the pace after 70 or 80 miles.
As other people have stated, ride your own pace. Do not try to hang on with a fast group.