Shimano Ultegra Shifters

Hi. I'm new to this forum. I have a question about replacing a Shimano Ultegra ST6501 shifter. I took the right one apart without knowing what I was doing and I cant get it back together. The bike is 12-13 years old. What Shimano shifter would be the right one to replace the ST6501?
Mike

 

FYI. You can replace your 6500 shifter with another 6500 series Shimano shifter OR any other 9-speed Shimano Road shifter which suits your fancy (Dura Ace, 105, Tiagra, etc.) ...

• in theory (THAT means that I have not tried it), you can use a pair of 10-speed Shimano shifters and then use the alternate rear derailleur cable position at 9 o'clock ...
• OR, you can mate a pair of Campagnolo shifters to our drivtrain ...

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Or you could convince a bike shop to break up a pair of new Sora 9-speed levers, or you could buy the pair and save the other one for when the other Ultegra lever craps out.