Answer to "Upgrade drive in 1st Gen TC or will power supply fail?"If it's lived until now, it'll probably be OK for a while longer. I have a WD Red 3TB drive in one - it just works.
Answer to "Random Mac Pro restart/shutdown"For anyone having this issue : Shut down. Pull out both RAM drawers. Remove all RAM. Remove all dust (preferably by dry compressed air). Carefully but firmly re-seat the RAM on the drawers. Re-seat the RAM-drawers in your Mac Pro. I've had this random shut-down issue right around the time Steve died, so it could also be related to his reality distortion field energy playing havoc on my Mac Pro ... but somehow I doubt it ;-) (The restart occurs after an unscheduled shutdown, if you have automatic restarts enabled in the Energy Saver preference panel.)