what impression does the narrator give of the church in his day?

Certainly the impression given is that the Church is corrupt. By the late fourteenth century Catholicism pretty much had all of Europe. The church became very wealthy ad it certainly wasn’t by giving all their money away. Cathedrals seemed to be made of gold and, to no surprise, the clergy were living rather well. Naturally criticism of the church grew among the people who largely lived in relative poverty. The Prioress, Monk, friar and Pardoner all represent the bloated and corrupt stereotype of the medieval clergy that we have come to expect. The Monk, for example, is a good example of Chaucer’s criticisms of the church. Monks in the middle ages tended to live in monasteries. They were expected to live their life in prayer, work and study. This Monk is loud and undisciplined. He can care less for holy devotion. Instead he enjoys hunting and eating allot (he is pretty fat!) The Monk doesn't wear the simple sac-cloth; rather he wears boots and furs. The Monk's character represents the disillusionment that many people had of the church as an institution.

After the Black Death, many Europeans began to question the authority of the established Church. Some questioned the institution itself. Specifically they questioned the corruption and hypocrisy. This is why Canterbury Tales is so heavy on the religious themes of piety and corruption. The Pardoner for example absolves people of their since, for a price! Chaucer's childhood was during the plague era which I would think affected his tale as well.