Tensioner is crooked and belt is sliding off. Can I do the job myself and how difficult of a problem am I looking at? Also what's a really strong new belt to get for the job?

 

Depending upon your mechanical skills, you can probably do this yourself. That said, it's important to know just what has gone wrong here. You'll need to find out what made the tensioner crooked, because I haven't come across this issue before, maybe someone else on here has.
When you say crooked, do you mean that it's actually bent or just not correctly lining up with the various sprockets and pulleys? A photo of the offending item would be priceless in helping you.

 

IF you bent the tensioner you may want to find the cause of the problem. its a pretty beefy part.

 

Nothing seems bent or broken just pully is loose is all. Just need to know if I have to pull the bumper and everything like the fan and whatnot. I'm still driving the car fine with no loss in power but the pully is definitely crooked and needs to be tightened. What do I do first lol

 

In your first post, you said the belt was sliding off. If the belt slides off, it will be disastrous. Period.

At this point we don't know which pulley is loose. If it's the actual pulley which is acted upon by the tensioner, you're going to have to remove the pulley and the tensioner, either replace or re-set the tensioner and then put it all back together. The front end needs to at least be moved into the service position to do this effectively.

 

I've taken off the bumper, radiator, and fans and I've gotten the tensioner off. O'reilys said the tensioner assembly shifted and a bearing in the pully has gone out. A new one is $100. Where can I find a cheaper one?

 

Google can help 99 1.8t accessory belt tensioner


VW Passat Serpentine Belt Tensioner - PartsPlaceInc.com