Honestly, it's probably not cost effective but I LOVE doing projects like this.

If it was my bike, the first thing that I would do would be to measure the distance between the rear dropouts.
A modern road bike is 130 mm. I'm betting that your bike is 126 mm. Now 4 mm isn't much - it's less than 1/4 inch. But it's enough to affect most of your planned upgrades. A new wheelset is going to be 130 mm. Brifters are going to require an 8/9/10 speed cassette rear hub - 130 mm. If you decide to spread the dropouts, I'd do it prior to repainting.

The next issue has to do with brake reach. If you switch from 27" wheels to 700c wheels, your brakes are probably going to be a bit too short. Again, if it was my bike, I'd "borrow" a 700c wheelset and test fit it in the frame. You'll be able to see what, if anything you'll have to do with your brakes and you'll be able to tell if the smaller 700c wheels are going to look goofy. Brake replacements might have new, nifty recessed brake nuts which will require drilling out your fork and rear brake bridge. That's another thing to do prior to painting.

Have fun.