That should be pretty straightforward to put back in running order.
You may have to replace the derailleurs as the plastic bits tend to crack with age, especially the front derailleur. You can get period-appropriate Simplex derailleurs on eBay for $30-ish, or used parts from a bike co-op for $5-10-ish. If the plastic isn't cracked, then go ahead and use the existing derailleurs.
You will surely want to replace all the cables and housing, and the brake pads, which will cost $30 or so in parts. Also the tires, rim tape and tubes, another $50-ish. Bar tape, $12.
The half hoods on the Mafac levers are rotted, you can simply run the levers bare, or there was a thread here showing how to cut some $10 Cane Creek brake hoods to closely resemble the original half hoods.
http://www.amazon.com/Dia-Compe-Cree...ke+hoods+black
The saddle is hideous and has to go.
Otherwise, it should just be a matter of disassemble - clean - re-grease - reassemble. Read the Sheldon Brown site to learn what to do. Be judicious, don't force a fastener until you are very sure you know why it is not turning, don't break or lose anything, you really want to re-use all the existing components. If you start replacing things, you'll get into the quirky world of old French sizes and threadings, and that will be frustrating. Be aware the non-drive-side pedal is reverse threaded.
You'll need a few bike specific tools (wrenches) which cost $10 each. Unless you have a co-op nearby that loans tools.
The bottom bracket will be a challenge because the cranks are cottered. If you have a LBS that will remove, overhaul, and reinstall the cranks and bottom bracket for a reasonable price, you might consider that. Otherwise, you can buy a cotter press or - people will get mad at me for saying this - if the bottom bracket turns smoothly, just drip oil into it (both sides) and ride. No, it isn't "right" but it will get you on the road and if you decide the bike is a keeper, you can do the BB later.
Some very fine sandpaper (like 600 grit wet/dry) will restore shine to oxidized alloy parts.
When (if) you get the frame completely stripped, call some local powder coaters. You can probably get the frame powder coated for $100-150, if you want to. At that point, I'd personally spend $50 for reproduction decals to do it right. It is your dad's bike after all.