Hello, I have never done one on the 3.4L motor, but I am sending you instructions from the GM service manual for the Venture. I hope that will help you. As for cleaning it, that will depend on how bad the carbon build up is on it. But if there is a lot of it, be sure to start the motor briefly with the valve off of the manifold to blow out any loose carbon pieces that may be floating around so it doesn't act up again right away. Thanks
Notice: Use the correct fastener in the correct location. Replacement fasteners must be the correct part number for that application. Fasteners requiring replacement or fasteners requiring the use of thread locking compound or sealant are identified in the service procedure. Do not use paints, lubricants, or corrosion inhibitors on fasteners or fastener joint surfaces unless specified. These coatings affect fastener torque and joint clamping force and may damage the fastener. Use the correct tightening sequence and specifications when installing fasteners in order to avoid damage to parts and systems.
Tighten the bolts to 30 N·m (22 lb ft).
Tighten the bolts to 25 N·m (18 lb ft).
Most time when you are having EGR problems, the stem itself or the electrical portion is what gets contaminated and causes problems. If you remove it and find a chunk of carbon stuck in the valve then you might be able to get away with cleaning it. If you have access to a scan tool you could drive the vehicle under heavy load and command the EGR valve all the way open. I use this method to clear out a chunk of carbon if it is stuck.... this way I don't need to remove the valve.
It is a tight fit back there, but as long as you follow the directions you will be able to get the bolts loose.
Below is a picture of the EGR valve to help you better understand where the bolts are.
Yes, it could be done but it would probably be easier to remove the valve.
The carbon deposits crumble under any sort of pressure, besides the very slight pressure inside the EGR valve. If there are pieces in the EGR then pieces have already gone through your engine so I wouldn't worry too much about it.