I would have said that you need to install the service on your development computer and then run the service locally, then attach the debugger to the running service. you must check the "Show system processes" for the process to show in the list, select the process and click attach. Next select the CLR from the available choices.
Please note you cannot debug the "Main" method, you might be able to debug the "OnStart" method, but it will be difficult. You could include a delay in the method to give you time to attach, though if this takes more than 30 seconds to start the start attempt wil time out.
If it is possible could you not put the code used in the service into a windows/console application to test and debug the code, once you know it works then move it back to a service.
Hope this helps