What model do you have?
If you want to DIY,spend $15.00 and get a Haynes repair manual. It will pay for itself the first 15 minutes you use it. I'm guessing you have a 123 (77-85 300D) by your description.
They cover this and a whole lot more. Armed with that and this forum,you can get into a whole lot of trouble!
84 300SD (sold)
[This message has been edited by Mr. BILL (edited 10-28-2000).]