I've never broken said part. (it's one of the only ones..that I haven't.)

I'd start by soaking the ever loving life outta the outside of it with PB or another penetrating lubricant. You need to try and break up some of the corrosion holding it in place. After a couple hours of soaking..then do your best to be gentle. Up and down movement can break the timing cover.

Since you haven't..you are a lucky SOB. Tyipcally it breaks the timing cover before the tensioner.