What is the process of transferring from the NG to the IRR?

If you have fulfilled your ADSO, you resign your post, submit a letter to your commander on why you want to resign and go IRR, have your commander submit a DA Form 4187 Personnel Action and wait until everyone signs off on it. If you still have an obligation, usually 3 years of OCS Officers and 3/4 in ROTC, depending on whether you were scholarship or not, your command may get a little harder to convince to let you go.

Have you gotten with your command and tried to work it out? Most Reserve/NG commands are fairly lenient and bend over backwards to help a SM especially when there is an education conflict. What exactly is the conflict with your employer? They don't have any choice about releasing you for the weekend a month and two weeks a year. They might not like it but that is law.