newb's first CNC mill (3040), advices

Just got this second hand. https://www.ebay.com/itm/US-CNC-3-Ax...YAAOSw7-palR5Y

(not exactly the same model as the above ebay seller but they all look the same generic china design).

The seller showed me it in operation and seems good enough for my personal usage for cutting and engraving 1.5-2mm acrylic.

To give an idea of my experience level:
I've never owned a small CNC miller but I've had 2 3d printers before and have had them disassebled/reassembled and upgraded parts, both all the electronics as well as the mechanical components.

So I guess my questions are these but if there are other things/advices you think I should know please also post.

1) What cutting speeds can I expect from this stock 300W spindle with 2mm acrylic?

2) There are some videos on swapping the spindle with a powerful but cheap dremel. is that a good idea? Besides the overheating/short lifespan and difficulties of controlling the rotation and speed in software I don't see why not.

3) What control software should I use?

4) The seller gave the CNC to me with a thick plastic slab bolted on the base plate. I guess its a good idea to keep it on so not to damage the baseplate? But is 40mm thick one maybe too much?

5) What mill bits to use and when?

6) Any obvious newbie dos/don'ts?