trying to replace my water pump. not sure how to remove metal by-pass tube from left side of old pump. need help quick.

Ithink you are refering to the heater fitting, Some of them just pull out and have a o ring that seals it. Ialways use some sealant when I install the pipe. Some of the pipes are threaded I think yours has the o ring. Just turn the pipe and pullout check first to see if there are any threades visable if there are just unscrew the pipe.