I posted a few weeks ago. I have a '73 Grand Prix that I have had for 25 years. I got it used. But had the same model as a teenager and sold it in college only to buy the exact same model a few years later. I am older now and decided to upgrade the gearing by installing a 7 "Megarange" freewheel and a compact triple crankset on the front as well as new derailleurs fore and aft to make it up hills. I spent a lot of time on the Sheldon Brown site and will tell you my difficulties so you can avoid them. The problem I had is I needed to get a new bottom bracket to take the triple. Here is what I did so you can do it differently and save some money:

1. Figured out that since the serial number is Nottingham and the original cranks were lugged, it was probably Raleigh 26 tpi threading which means that you can't just install a new cartridge.
2. Tried to find a spindle that would take the triple only to find they are virtually impossible to find (series 7 or 5 square taper)
3. Ordered a Shimano UN 72 cartridge which is no longer sold from someone on ebay. It is unique in that the cups remove (with some difficulty) and can be used in the Raleigh BB w/ Phil Wood rings from Harris Cyclery. Alternatively, for $150 you can get a Phil Wood BB which my budget wouldn't allow.
4. Installed the Phil Wood rings myself and probably, inadvertently, installed them backwards which basically meant I tapped new threads w/ the rings (I hope not but they were hard as hell to put on).
5. Got it all working but now, for whatever reason, the pedals are too wide apart and it hurts my knee
6. Trying now to rectify the problem by having my trusty bike shop tap new threads (hopefully I didn't ruin the chances of that by installing the Wood rings)
7. And, assuming they can, installing a shorter Shimano cartridge. I have my fingers crossed.

Bottom line is that I have spent far more, in bits and pieces, than logic would dictate. The upside is it has been very satisfying emotionally and I got my hands dirty with bike repair again since teaching myself the basics in the early seventies. Now I am looking wistfully at old bikes on Craigslist wondering how I can sell my wife on getting another bike to fix up. I have two already '97 GT Aggressor MTB from Craig's list and the Grand Prix. Not sure what to tell her about a 3rd or 4th.

So, if the mood takes you, paint your bike. The Grand Prix may not be a Motobecane, but it is a bit of history.