To remove excess solder or to clean the legs I use desoldering wick/braid (bought at radioshack).
I don't know of a place that sell V7 motherboards, I've seen v4 and below, but not v7. I guess you can try ebay.
If you can't fix it many people on this forum have recomended Bill from
www.freedomlives.com for PS2 repair. He might be able to fix it.