What is the main difference between regular chocolate and baking chocolate? 

usually baking chocolate has lower sugar content and higher cocoa and cocoa butters. Papaginofoods Inc carries a large collection of fine baking chocolates with different compositions of cocoa and sugar from best brands in the chocolate world like Callebaut, Cocoa Barry and Valrhona. 

How to change a recipe calling for baking chocolate?

Dark/Semi Sweet Baking Chocolate	Milk Baking Chocolate
White Baking Chocolate	Dutch Processed Cocoa Powder
Flavored Baking Chocolate