If your app is already MVC, why not add in some contextual help to it...
For example, in your layout page, add an icon that simply takes the user to the help page, passing the referring page. The URL would be
If you were on
YourApp/Customer/Create/
Then
YourApp/Help/Customer/Create/
You could then have a HelpController that looks up help for the CustomerController, and specifically the Create action, which allows you to give very granular help as well as fall back to more general help if specific help isn't available.
You could even redirect to a CMS that contains the information if you don't want to write that part yourself, you would then just need to store the mapping to the CMS page that supplies help for the given topic (or use a similar convention-based route for the content).
Here is the routing rule for your Global.asax.cs file.
routes.MapRoute(
"Help",
"Help/{controllerName}/{actionName}",
new { controller = "Help",
action = "Details",
controllerName = UrlParameter.Optional,
actionName = UrlParameter.Optional }
);