timing belt tensioner

I have a 99 cabrio (2.0 L )that has a what appears to be a noisy timing belt tensioner(a lot of squalling noise from behind the belt covers). Can you change the tensioner without changing and or removing the timing belt? I have the older body style 1999 vehicle, so I don't think I have the thermo tensioner. Or do you recommend changing both belt (belt has 40 k mikes on it)and tensioner at same time as long as you have it opened up? I do a lot of my own auto work but haven't tackled a timing belt job before - any tips on doing that particular job? Any gotcha's to look out for? Any help appreciated.