Medieval! (Or mediaeval)
Carolingian!
Argh!
Sorry – I am a mediaevalist, and my main field was Carolingian Europe (Louis the Pious) – ‘medieval’ is one of those words that gets misspelt all over the place (‘mid-evil’ is another one), and it drives me bonkers. 
Anyway. All aspects of Carolingian life were inextricably intwined with Catholicism, so just about any study of any facet of life then will necessarily touch on it.
Here are some books you may find useful:
Rosamund McKitterick The Frankish Kingdoms Under the Carolingians 751-987 — an excellent ‘here’s what happened’ and ‘one damned thing after another’ basic history of the period.
Rosamund McKitterick The Carolingians and the Written Word which is a study of literacy and use of writing in the Carolingian period. If you were literate, you were probably – but not necessarily – a monk or a scholar. This book talks about charters, law codification, book production and ownership of books, and the education, audience, and patronage of the laity for books and scholars.
Henry Bettenson’s Documents of the Christian Church is a wonderful annotated source of Christian documents from the earliest times through the 20th century, although the emphasis is on antiquity and the Middle Ages.
Even better isP D King’s Charlemagne: Translated Sources. King has excerpts from the many yearly chronicles and annals, The Astronomer’s Life of Louis the Pious, capitualaries (laws), and bits and pieces of other narrative sources.
And a terrific overview of everyday life is Pierre Riche’s Daily Life in the World of Charlemagne. Riche covers the geography of the Carolingian empire, what it was like to travel, the forest, town life, the monastic communities, palace life, demographics (birth rate, morality, etc); Aristocratic life, wealth, sports and entertainment, court life; the ecclesiastic life; the ordinary people. He covers rural technology and farming, artisans, builders, furniture & clothing; houses (lighting, heating, hygiene), food and drink. And the final section is on religious belief and attitude, covering paganism, socery, magic and astrology, and also the religious training and instruction of the clergy and laymen.
For a life of Charlemagne, Einhard and Notker the Stammer’s biographies are readily available in translation. For Louis the Pious, there are three biographies written at the time, the Astronomer, Thegan, and Ermoldus Nigellus. I believe the latter two are readily available in English translation. Ermoldus has been published in French (and not very accurately); there is an English translation, but that would be my disseratation :D.
The rule of St Benedict is a good basis for monastic life; it was an ideal, though, that no one managed to achieve. You might look for the Plan of St Gall, which was a monastery to be constructed during Louis the Pious’ life, what was planned to be the ‘perfect monastic community’ based on the Rule.
Start with Riche, then McKitterick; you can follow up on primary sources from their bibliographies. There a a great number of poems, epics, laws, biographies, etc that survive from this period. I don’t know if you read Latin, but there are many, many saints’ lives (hagiography) that can be found in the MGH. The only difficulty there is they all follow a set pattern – called a topos – in which every saint shows signs of sainthood as a child, or many saints perform the same sorts of miracles.
You might also look for translations of contemporary sermons, because they were preached to the ordinary person, and read rather folksy as compared to the theological discourses – St Augustine’s sermons, for example (5th century) or especially Caesarius of Arles sermons (many of those are translated). You find out what the common man wanted or needed in his religion; Caesarius used to complain that he had to lock the doors of his church to keep people from sneaking out whilst he was giving the sermons.
Unless you are absolutely set on the Carolingians, you might go a wee bit backwards in time to the family who ruled prior, the Merovingians. Get yourself a copy of Gregory of Tours History of the Franks for a read about a right nutcase family. Had I had my way in graduate school, I would have focused on them, not boring old Charlemagne!
Hope some of this helps.
