How to find all interfaces, properties, and methods in an assembly

My main question is, how to I get all interfaces in a known (referenced) assembly? The follow up is how to I get all properties and methods for each of those interfaces?

Context, if you care

Working with a third party we receive some COM objects and run tlbimp.exe to get .Net objects. Thus far the APIs have always matched and it is preferred by our internal customers to code against one API and not have to worry about the changing references. For this reason we wrap the tlbimp output in our own namespace and build adapters.

What I would like to do is ensure that the APIs are indeed the same programatically. To do this, I would like to query the known assemblies for all of their interfaces and methods and properties on those interfaces. It is then trivial to compare one collection to the other to find any gaps.