Mine weren't cracked but they were lightly seeping out onto the engine, and I would get a single drop of oil every now and then. It was noted during my PPI and I replaced them about a year later.
If you lift the back of the car and look up under there you can see the coil packs, and that is where you would see the oil seeping out if they were leaking.
When changing them, you can remove the rear wheels and the inner fender liner and the access is right there. The one closest to the front is a little tougher to get to but I think there is a 2nd fender liner to the front that you can remove to make that access easier (or maybe that is the only one you have to remove, I can't recall...)
Not a bad job to do. I used a right angle threaded pipe fitting lightly screwed into each tube and they came out very easily. When putting the new tubes back in, I used the other female end of the fitting to rest against the tube and push them back in.
I wish I had the size of this elbow but I do not, but if you buy new tubes just take one to Lowe's or home depot to test fit. I think 1" maybe?