Getting at basic SCM info

Just a couple of questions:

I want to progmatically open a file in the repository; specifically given a repository workspace and a relative file path within that workspace, how can I request the file from the repository and open it in an editor?

Also, is there a simple reusable Component Selection dialog I can use? I want the user to choose just 1 stream/workspace component.

The code should run in both RTC 1 and 2.

Thanks for the help!