Having done this twice before, I strongly, STRONGLY recommend picking a colocation center that's less than an hour drive from someone who works for the company. Or you.
Just in case, but that does come up from time to time and if it's many hours away (or worst of all an airplane ride) you will get hours/days to fix things as you noted.
The shop I worked with, we had support on the machines, so Dell would send a tech out to replace a part for the servers that had valid support contracts. We still needed someone on the phone to remote-in to test the fix, of course.
For more complicated problems, our main colo was about 45 mins away from almost all the SAs. We used remote hands for colos that were an airplane ride away, and had varying (read: sometimes really shitty) results.
Just in case, but that does come up from time to time and if it's many hours away (or worst of all an airplane ride) you will get hours/days to fix things as you noted.