I'm sticking my neck out here, and it's just my opinion.

Q. Will it work?
A. There's no reason it shouldn't work.

Q. Where is the best place online to get a 700c rim, and what should I be looking for in this application?
A. I've had good luck ordering rims from Harris Cyclery. Mavic Open Pro rims are nicely built aluminum alloy rims, but may not have the vintage "look" you're after. Removing the decals from the rims would help achieve a vintage look.

Q. What size spokes should I use?
A. I'm partial to DT Swiss double-butted stainless steel 2.0/1.8/2.0 "Competition" spokes, but again, these may not achieve the "look" you're after. The length of the spokes will have to be determined from the lacing pattern you want to use, the ERD of the rims, and the hubs you use. Use Damon Rinard's spocalc to calculate spoke lengths.

Q. Is that Bendix in the auction indeed a 36 hole model?
A. The seller doesn't say. You can guess by trying to count the holes, but the only way to know for sure is to ask the seller.

Here's a 36 spoke 3-cross 700c wheel using a Mavic Open Pro rim, Campy Record high flange hub, and DT Swiss Competition 2.0/1.8/2.0 stainless spokes. The rim decals scream "21st century", so you'll probably want to remove them.