350 watts should be enough for that setup. Do you have any info on what type of AGP slot is on your motherboard? The 5200 video card needs an AGP 8x slot, and won't work in an AGP 1x or 2x slot, and may work in an AGP 4x slot.
As a side note, a GeForceFX 5200 is not going to last very long as a gaming card as it's already slower than the previous generation of video cards like the Titanium 4200. The 5200's are severely stripped down versions of the mainstream cards.
goates