HelloCustomer The tensioner for the alt. belt is located directly to the right of the alt. Loosen the nut on the front of the pulley and there is an adjustment bolt that is below it. Rotate and you will change the tension on the belt. As for the plug, it has a release tab that you need to depress. After removing the belt, remove the bottom bolt on the alternator, dislodge it from it's spot and rotate it so you can see the plug. You will see how to remove it at that time.
Your JA Expert,
I don't have a good picture of the connector so we'll try this together. Do you have the replacement alternator yet. If so, look for the locking tab on the new one and index it to yours. If not try inserting the screwdriver in various points around the connector and put pressure to push the connector down. Let me know if you see something