As LH mentions.. it is recommended to check the pressure before replacing. Standard pumps seem to cost around $100-120 in my area. A failing fuel pump isn't normally viewed as contributing to excessive fuel consumption, if anything it may run you lean.
GM pumps are known to be noisy, and I've experienced a serious increase in noise before the drove me to change out the pump. Never failed..pressure checked out.. sheer noise level was too much to handle.
On the fuel consumption.. you may want to consider when you did your last tune up and how many miles are on your O2 sensor.
00 Regal GS: All kinds of cool stuff.