I think I have a bad u-joint. All I need to do it check for slack right?
And are there some upgraded ones I can put in when i change them?
And are there some upgraded ones I can put in when i change them?
For the $40 it'll cost you to put in a good set of U-joints, don't waste your time taking the old ones out and putting them back in. Just replace them.

Yes. you will want to orient the zerk so that as the DS turns, it gets compressed between the shaft & differential yokes.if a guy is stuck doing greaseable joints, you want to have the zerk fitting in one orientation, don't ya? It has something to do with the direction of loading or something to that effect IIRC. Does that ring a bell? It's something I thought I once knew but cannot remember anymore.
Yes. you will want to orient the zerk so that as the DS turns, it gets compressed between the shaft & differential yokes.