I have a large DEM (DEM1) and a clipped one(DEM2), I want to replace a specific area of the large DEM with the )clipped one (see image below)

heres some high level steps:

• clip area of DEM2 out of DEM1
• if DEM1 is a different cell size, resample to match DEM2
• then use the rastermosaicker to combine them
• write out to output file

A big assumption here is that the scale of the elevation values are the same. If they're not, then you'll have to rescale either DEM to match