C# share reusable library

Question

I have a C# 2008/2010 application that is currently accessed as an exe file. I would like to change the application that calls the program in a 'faster and/or better' manner. To accomplish this goal, I could move the logic of the app I am starting with into a reusable library.  Then rather than calling the other program I could simply use the reusable library in the app.

The code in the calling program currently looks like the following:

strConsoleAppLocation = ConfigurationManager.AppSettings["dll_location"];
string Process_Arguments = null;
Process RPT_Process = new Process();
RPT_Process.StartInfo.FileName = strConsoleAppLocation;
Process_Arguments =  " 7 " + strCUSTID + " 1";
RPT_Process.StartInfo.Arguments = Process_Arguments;
RPT_Process.Start();
RPT_Process.WaitForExit();
RPT_Process.Dispose();

My goal is to share the same reuseable object and pass parameter values to methods that are exposed. Let me know what I suggest is a good idea or not? Also can you show me some code on how to accomplish this goal?