Excellent thread topic John,
The joy derived when an old neglected item is back to life is what keeps me going. I do my best to mend vintage coin operated stuff as well. On a good day I'll get "that looks better then it did" from the wife and maybe a profit. I'm just happy it works and looks as new.
Buy the best original complete kit you can afford. Look for hardware with no pitting. Other than re-plate can't fix that. Take a bunch of pictures. Then take some more. The lock washer that is bigger then the rest goes on the throw...
Look for an incomplete MIJ set that needs whatever skill you want to practice. For $30-$50 will get that done and may well be able to sell the extra parts.
Biggest thing is never get in a hurry and cut corners. Only stewards of the vintage gear. I just try and put everything back to factory hoping it will still be enjoyed another 70 years hence.
Haven't run final numbers on my RK restoration. 1K is close. Period correct parts are spendy. Hope of some help.
Creighton