Yup. An hour job at the most (and that's if you end up mopping up spilled coolant).
My leak ended up being right where the coolant tubes enter the heater core body. Even though I already had a new core purchased, my old man braised the crack in the tube while I was away at school so it was good as new. I suggest that you check to see if a small crack such as this could be the source of your leak as well. If so, you might just be able to save yourself $30 and just repair your current heater core.
'87 GT 3.4 pushrod daily driver
'88 GT 3.4 DOHC swap in progress
[This message has been edited by Irrationable (edited 12-15-2014).]