First, yeah. Well, sorta. The video card change isn't going to help much at all, the GF4/MX is a slightly warmed over version of the GF2/MX you had before. But the move from the one gig Celly to a 1.7 P4 should give you an improvement you'll be able to see.
About your mobo, that's an older one and I had to do some digging. Its built on the original 845 chipset, which is better than the old Socket 423 boards used before. But the first round of 845 boards didn't offer a lot in the way of overclocking, like the later 845E boards do.
Looking at the .pdf of your owners manual, I see that you can dial up the FSB and memory speeds, and lock the PCI/AGP speeds, but that's it.
I haven't tried to overclock that board. But taking a semi-educated guess, I'd predict that with good cooling and airflow you'll be able to wring a little more out of the system, but not as much as you'd get with an 845E board.
BHD