Don't give up quite yet, let me get home and verify that I have my commands right, I'm doing this from memory. Zax was helpful in confirming that I was right, but I just want to make sure.

Oh, before I forget, the most you'll get out of the stock setup, in terms of rpm, is about 5000 rpms. You can bump that up, by using a 24v power supply, but I would only plug that into the motor itself. Of course that means bypassing any speed control. Do not plug 24volts straight into the board. This would get you about 10,000 rpms and a bit more torque. IMO, it's often better to run as fast as you can.

Thanks, yah, I've been focused on 3D printing, so a tad rusty on GRBL commands.

Ok, so first up, we need to determine what values are set for your spindle speed parameter. Type $$ in a command line interface. We're looking for line $30. If it says 255, for example, then you can set your speed between 0 and 255 and use a command between those numbers.

Now, you should be able to turn on and off, your spindle speed, using the following command:
m3 s255
Sets full speed

Or, you can vary that, by typing a lower amount
m3 s200
Sets partial speed

m3 s0
turns off the spindle

Now, why do I mention that? Because you can edit your gcode before you send it off and make adjustments before you start. I will admit, I am a bit rusty, so I may have the commands slightly off, but I am at work, so I can't test, but I have had great success modifying my speed this way. Will test later today when I get home. But this gets you a head start on what to look for.

Edited for clarification.

RPM speed is set by gcode, I forget the exact one, but give me a bit and I'll find it.

You might want to rephrase, not sure what you're asking...

A bit late in replying, but leveling your mill is fairly easy and difficult at the same time. Just time consuming, mostly. First thing is to have a flat, clean, level surface to work with. You'll have to loosen up all the bolts, then working your way up, from the bottom to the top, checking everything for squareness. If you need to, use a 3" or 4" machinist square. When tightening the bolts, both sides have to be the same distance, so be careful when tightening, that they haven't moved. This process may take many tries, but it can be done.

This machine will not natively engrave in the fashion that you described without heavy modification. Could it be possible? Maybe, but I think you'd get the same results using a V bit right out of the box.

Yah, I'd be happy to, I have something similar planned, can easily include that as well.

That's ok, I've upgraded mine to 1.1 as well, but the command table is the same.