This sprinkler <i>will</i> work.
Yes where the solenoid previously existed, you block that hole with epoxy. Then drill a 7/16" hole in the center of the lid so that you can tap in a 1/4" NPT fitting. Then only screw the fitting until it is flush on the interior of the lid. This is not to as distort the stroke of the spring, and flexing diaphragm.
Although it sounds as if you do not have a abundance of money, you can purchase the typical 'Green' WaterMaster Orbit valves for around 12$ locally. They do not have a spring, and the lid is thicker allowing for area to thread into.
I would not suggest silicone, rather some hard setting epoxy.