I'm not sure. I wish I had a Kill-A-Watt meter to see what the setup is using for power...not very much though...you can hear it in my generator when I fire that 400w MH up! Same here...but in my case if it tripped the whole house would go dark, much to the annoyance of other people, so...
Yeah I bet people had their phones out filming that thing..."Fluorescent Light Epic Fail"!
That ballast would make that BIZZZZZZ when it was arcing really bad in this case too...
I had a 3500K Sylvania Octron in my bathroom light die earlier this year with the purple glow. I leave the light on in there a lot and I was going in and out so I didn't get to witness the very end...but like an hour later I went back in there and noticed it was out, so I stuck a pair of 34w T12 GE Watt-Misers in there since I didn't have any extra F32T8 lamps at that point. They work fine so even though I later found a pair of T8 lamps in the trash along with that F40CW Mainlighter I have (the working one) I've left them there. When they die I'll stick T8s back in though.
If it were me I might leave the existing bare-bulb ceramic sockets there, and tap into their junction boxes from up in the attic to run Romex to the new lights. I would suggest mounting them perpendicular to the joists, with long enough screws to reach into the joists pretty far so they can't pull out of the drywall. Drywall screws work just fine for this. So you'll have the existing incandescents plus the new lights.
A stud finder is the best way for sure although I've never used one. Knocking on the drywall can give you a ballpark idea too, between joists it will sound hollow. Climbing up in the attic to see what side the boxes are on is another surefire way IMO since the joists should be on a standardized spacing of 16 inches or 24 inches on center (from the center of one joist to the center of the next). So you could measure it out from there. If it's not enough you could screw a wood 1x... plank to the ceiling into the joists and mount the light too that. This would be a good idea for a heavy preheater or something...
Which fixtures do you plan to use?