I'm not sure if our ports are the same. I pulled and resealed a aft port this past weekend. Mine are screwed to the cabin like DannyS said. Its a pretty easy job, just take your time and go easy, once the screws are out it should pull away from the sealant.
Here's a tip for easier clean up. Use some of that blue painters tape and tape around the port so the tape is on the cabin as close to the port as you can get it BEFORE you remove the port. This is so when you put the port back on with the new sealant, it will keep the excess sealant off the cabin. This allows for easier clean up after the port is installed.
The hardest part of the job was cleaning the old sealant off both the port and the cabin. I used a razor blade and WD-40. If you can't get the DOW 795, you can use a good marine grade black silicone sealant, Boatlife makes some. Use marine grade Silicone (not caulk).
When putting the port back in, don't over tighten the screws, I tried to run them in evenly watching the silicone as i tightened and stopped once it started squeezing out. The screws are there to hold the port while the silicone sets up. If you tighten them to much it will squeeze out all your seal and possibly crack the port.
After 24 hours use the razor and clean up the silicone that was pushed out as you tightened the port. The tape you put around the port before you removed the port is now your best friend.