I recently came into possession of an older Trek 700. I planned on doing a fixed conversion but the frame is incredibley rusty -- this is one abused bike! I still hope to use the wheelset, which is in pretty good shape, except that some of the eyelets on the Matrix rims are rusted, and one on the rear wheel has actually come loose. How vital are these to the integrity of the rims? Can I true the front & redish & true the rear and just ride on 'em, or do I need to replace the spokes and eyelets? And where can I even find replacement eyelets? Any thoughts or experience from someone whose come across a similar situation would be welcome!

its prob not worth it to replace an eyelet (if it is even replaceable)
its best to just crudely true it and then proceed to ride the wheelset into the ground.
Then just take all the money you saved yourself and buy a decent wheelset such as the ever-popular deep V/formula hubs.