I think under the circumstances that a general confession would be prudent.
If you can, I'd try to attend an Ignatian retreat. The SSPX has several retreat houses that have regular retreats for men and women.
As far as wiping out your known & unknown sins -- that's only if you were an unbaptized pagan and then were baptized when you were 50. Just going back to Church doesn't wipe out any sins. And only the sins you confess are forgiven -- though your confession has integrity (you receive forgiveness for the sins you confess) if you honestly forgot or were not mindful of one or more sins. So if you forget some sins, you still made a "good confession" but you should confess those newly-remembered sins next time.
When you've been away from the Sacraments for a while, it's good to read a short booklet or some other material to help prepare for a good general confession -- then you can start your new life with a clean slate. I think that's very important.