Congratulations on your new career! While I'm not a shop owner, like you I'm focused on mastering the trade. You might want to review...

Principles of Bicycle Retailing III
by Randy Kirk

Brief Description: Featuring 12 chapters on all aspects of bicycle retailing, this manual by Randy W. Kirk contains the latest information and expands on the sales, marketing, and bike shop business advice contained in his previous two popular bike retailer books.
Now regarded as THE ultimate resource on bicycle retailing, Principles of Bicycle Retailing III (ISBN No. 0-924272-05-8) thoroughly discusses the importance of profitability in the bike store. Detailed samples of Income and Expense statements, Profit and Loss charts, Cash Flow Analysis, Sales Goal charts, Customer Sales Letters and Newsletters provide invaluable resources to use in starting or running a successful bike business.
Included in this 207-page book ($19.95, illustrated) are chapters on computers, proven sales techniques, business planning, marketing, purchasing, and a sample employee manual. This third edition is the companion manual to the original Principles of Bicycle Retailing II.
Price: $19.95

Source: http://www.infonetpublishing.com/kirk1.html

Also please check out:
http://www.bicycleretailer.com/bicyc...iler/index.jsp
for an appreciation of the state of the industry