This is a dealer-only item, besides if you can't get a NOS T-3 lamp, nothing else is acceptable. Might need to sell it.
This is easy. The plug on the back of the headlight pulls straight off. Look for loose wires or corroded contacts while you have it off.
Most auto parts store have replacement connectors if you need it.
Most auto parts stores carry the replacement bulb too. It's a sealed beam, ~$5-7. It's held on by 2 or 3 small screws thu a chrome retainer into the headlight bucket. These screws are easy to strip out, so might wanna use some penetrating fluid to help break them loose.
If you have to have the T-3 original beam, some of the popular repop house carry them, but they are more $$$$.
Have at it.