Hello Sebastian,
The way that you have worded your post, would certainly make anyone hesitant to comment on your belief, not wanting you to feel unwelcomed, or unaccepted in the Church. But to point out the errors of Islamic doctrine, Mormon doctrine, and the doctrine of Jehovah's witnesses, (as many have in other posts), without also pointing out the grave errors in Catholic doctrine, when such doctrine becomes an issue, as it has here, would be somewhat discriminatory and biased.
My friend, if you have fully accepted the doctrine of your church, you believe considerably more than what you've stated here concerning Mary and your church.
In the Councel of Ephesus in 431 AD, your church determined that Mary was the mother of the whole person of Jesus Christ, making her not only the mother of Jesus in the flesh, but also the mother of God, which also serves to support the Catholic belief that Mary is the mother of us all.
It is also known that Mary was a virgin at the time of her conception, but continued to have children after the birth of Jesus. This is well supported in the scriptures, however the Catholic church has made her a 'Perpetual Virgin', claiming that she never lost her virginity.
It is also Catholic belief, that Mary was sinless. The only thing that remains a matter of debate in circles which support this claim, is exactly when she became sinless.
According to the Ad Caeli Reginam, by Pope Pius Xll, Mary is the "Queen of Heaven". This is a belief based on the assumption that because Jesus is a King, Mary certainly must be a queen.
Friend, I agree that no one is in a position to judge the salvation of another, however, this belief system is certainly not consistent with the fundamental beliefs of the bible It cannot be said whether these serious errors in doctrine could prevent someone from being saved, but, I believe that anyone choosing to question this doctrine is wise to do so, as scrutiny is definately warranted.