I opted to get the heater core replaced after helping a buddy do his, it took us over 2 weeks to get it all figured out and a lot of swearing.
the entire dash needs to be removed, it's not a one-day job.
Personally, even after taking it to a local shop to get it done if/when it goes out again I'm taking it to the dealer.
The local shop told me they had a hell of time with it and based on all the rattles and extra screws I found afterwards I'd have to agree.
I did remove the outer dash to find homes for most all the screws but even that was a PIA.
once the shop removed the original heater core, they showed me how the core that was in the Jeep did not have some additional bracing brackets that the replacement core had. Without the brackets it was allowed to move too much and the stamped fitting basically worked loose and that's where it was leaking from. the core itself still looked brand new.
if you decide to do it yourself, watch the wiring harnesses, forgetting to plug something in will ruin your day...