Chosen Solution

Is this just just referring to reapplying thermal past or do I need to buy new heatsinks as well

Two things. For all intents and purposes, the motherboard IS the PS4. If you’re convinced that your motherboard needs replacing, it makes a lot more sense to just get a different PS4. Secondly, if you were to replace just the motherboard, you would be able to use all the parts from your PS4 EXCEPT the daughterboard. Since you indicated a release model, you would need the matched daughterboard to the motherboard that you’re buying. Otherwise, you will not be able to run PS4 games.