The reason that you would want to upgrade your air assist is to have cleaner cuts. This will also help somewhat with engraving but the biggest benefit is seen when performing a cut operation.
Installing your own DIY system is pretty straight forward. You will connect a compressor (preferably an oil-free quiet compressor) to a regulator, then a solenoid that will be controlled but the laser controller. From the solenoid the system will then be tied into the lasers stock air assist. I will provide a parts list and video below.
Parts (Affiliate Links):
Compressor
Regulator
Solenoid - Make sure that you are getting a 24v DC solenoid Alternative Solenoid
Wire
1/4 Quick connect compressor fittings
1/4 connectors NPT
All of these products and alternatives are listed in my Amazon Affiliate Store