Is it true that St Augustine saw marriage as inherently sinful because of original sin being transmitted? what does the Church say? maybe that statement is an oversimplification of St Augustine?
Saint Augustine thought marriage was a good and that continence was better for those capable of such a life. This article may help:
No. It is not true nor accurate.
I need to read what he said but I know for a fact that it is not true. Quite the contrary.
As far as the official stance of the Church I recomend reading the following;
The Catechism of Trent, followed by Balltimore Catechism followed by the Cathechism of the Catholic Church. (In that order)
As far as to St. Agustine you will need to read his works in relation to this topic.