The best confessions come from the Holy Ghost, so pray to Him to enlighten you about your past sins and even to take over your will and your heart when you are receiving the sacrament.
Find a good traditional examination of conscience to set the stage. Here’s one I just found, but you may like another one better.
http://www.fatima.org/essentials/requests/examconc.asp
That said, I wouldn’t get hung up on cataloging every venial sin. I would concentrate on any mortal sins, particularly whatever is most gnawing at you. You can even ask the priest for help covering the bases since it sounds like you’ll have a bit of time with him.
And, of course, expect to walk out of there lighter than air!! Some of the posters on here don’t realize what a powerful, powerful grace it is to humble yourself before another human being. There is a reason that Christ gave the power to forgive sins to the Apostles—He understands human psychology better than we do!
And be assured of my prayers....you really made my night with this post. :)
Roman Catholicism continues to seemingly equate God and Mary as being on the same level.
There is nothing, repeat nothing, in the New Testament about giving any worship or praise to Mary, the Saints, the Roman Catholic Church, etc....it is only about worship and praise to God.