My MBP had a noisy right fan. Probably "imbalanced" or something.
Super smooth. The fan was easy to replace.
Pull the fan connector from the logic board "upwards", not forward. There's not supposed to be any real resistance. Don't pull too hard if it doesn't give in. I messed up my fan connector on my Mac Mini by doing that - pulling to hard in the wrong direction. The fan connector on the logic board is really the only thing you can mess up here.