92 Celica Vibration

I have been having trouble with my 92 Celica GT (manual) vibrating. Not when I first start it in the morning but usually at the first stop light and every stop light after that. The steering wheel, seats, and pedals all have a slight vibration and I can visually see the hood vibrate slightly. When the headlights are on, the drivers-side light vibrates as well. This is all only when I am stopped and idling, in nuetral or in gear with the clutch down.
So, based on what I have read on a some other posts here, it seems that the likely problem would be the Motor Mount. I have also read that adjusting the Idle RPM may help.
And based on that I have two questions.
First, if it is a motor mount problem, any ideas on how much something like that cost to fix by a mechanic. I would need someone else to take care of it and I have a limited budet.
And second, it seems to be a fairly easy procedure to adjust the RPM (from what I have read). Any basic instructions on how to do this. I certainly know my way around the engine just not specifically this process.

thanks

Dont pay a mechanic to change your motor mounts. All you need to do is take a look at them (with the engine still in the engine bay mind you) while the car is running and visually inspect them to see if any of them are loose or vibrating uncontrolably. If you find that one of them is bad just buy a new mount...go to your local allied rental center and rent an engine lift for the day. attach the lift and adjust it so that the chain is TIGHT as in almost lifting the engine. Then change out the motor mounts.

Well, I am really not mechanical enough to do that. Or maybe I could with someone showing me. So, since I need to have a mechanic do it for me, Anybody have any idea on prices??

And beyond that... I can easily get rid of some vibration when my engine is running at a little bit higher RPM. Anybody want to tell me how to adjust this. It is vibrating at about 700rpm right now and seems ok when at about 850rpm or higher.

i had the same problem with my 90 celica. do u know if the rubber gromets on the fuel injectors have ever been changed? if not change them. im talking about the gromets that r on the bottom side of the injectors. some times they get stuck in the head so u have to pry them out w/ a screw driver. mine were so bad that they broke apart when i pulled them out. change those and that will probably fix your problem.