Although it’s been on shelves for a while, iFixit recently performed a teardown of the M3 iMac, and to no one’s surprise, the internal design and components are a lot like that of the M1 iMac it replaced. The one major change (besides the System on a Chip upgrade) is that the new iMac now uses a single Complementary Metal Oxide Semiconductor (CMOS) battery instead of the two that were in the older iMac. (A CMOS battery is used in desktop Macs to store data in the motherboard’s BIOS and usually lasts many years without needing to be replaced.)
Besides that, everything else about the M3 iMac is like the M1 iMac, which iFixit tore down back in 2021. The innards of the iMac are dominated by two grill chambers, and the connector to the stand has a lot of screws. The motherboard takes up a small amount of space at the bottom of the case, and the ports are housed in modules that are easily replaceable.
Apple uses an adhesive to attach the display to the case. The adhesive can be easily removed and replaced, but it’s not as simple as the magnetic attachment that was used in the Intel-based iMac. iFixit gave the M1 iMac a repairability score of 2 out of 10 (10 being the easiest), but they haven’t published a score for the M3 iMac, which would likely get the same score–we can’t imagine the CMOS battery change would influence its opinion much if it all