I did both because if you're doing the primary and can afford it, may as well do the secondary because it has to come out. I also did thermostats while I was in there. I'm a fairly novice wrench and it took me about 6 hours because every bolt I removed I taped to cardboard and wrote where it came from.
Assuming you have it done it before, a good tip that helped me was that I drained the radiators the night before, while also removing the grill and headlights - it's easy and gives you a boost of getting directly to work the next day.
This video, ironically, by Mishimoto was very helpful for the process. I used Ford coolant, though.
https://www.youtube.com/watch?v=LZlbKb8hk30