Replacing valves is not all that difficult ... just time consuming. The manual valve (discontinued quite a while ago) is sealed in with a calking compound that precludes the installation of any other glues in the area. That means that you need to remove that material before installing anything else in its place.
First step is to draw a circle around the original valve and cut the material out. This effectively removes the caulk. Then cut a matching circle out of new material (I'll send you some) to act as a patch. Then cut a bigger circle and glue it on the inside ... shiny side to shiny side. This is going to be your backing. Now fill that hole with the patch that you cut. When you have completed this, you should have the hole filled in and the suit structurally sound.
Next, glue the valve gasket ($14) onto the patch area. You will be able to see the nylon from the center of the gasket. With a sharp knife or scissors, remove that material. That's where you will be installing the valve.
Finally, apply a very slight amount of silicone grease to the face of the valve($138) and insert into the gasket. Make sure that the groove on the gasket is lined up with the ridge on the valve. On the inside of the suit, install the delrin friction ring and then the backing plate. Screw down hand tight.
NOTE: Only use PB-300 glue ($20) for this job.
Another option is to have your dealer do the job. for liability reasons, we can only do it at the factory if we install both the inlet and the exhaust and your Scubapro inlet valve is pretty much trouble free. Plus, the total valve job runs about $300 ... a lot of money for an old suit!
Hope that helps!
Just my $.02
RayC
http://www.ossystems.com