Heater core question?

I have a 97 Cherokee. Since it has started cooling off I used the heater finally the other day. When it first starts running it has a sweet smell (antifreeze). After a few seconds of it running the smell goes away. The heat is warm and have had no issues with it not working.
Is the heater core on its way out or could there be another issue?

Thanks

There could be another issue, but I would bet if you took the box out and opened it, there would be coolant in it coming from the heater core.

First See if u have any leaks on the passenger floor.
Then pressure flush the core itself in both directions,while checking again for leaks.
If it leaks replace the core.

How hard is it to replace the heater core on a 2000 XJ?

It requires you removing the dashboard.