It is not uncommon for there to be a surge of water out the top as the thermostat opens, it'll puke some then, the coolant will then settle to about an inch or so below top, and circulation should be visible from the opening .
The other overheat thread currently running has just had his plugged rad cleaned, and we're waiting for results .
You'll be fine .
If you want some comic relief, scan some of the older threads, some truly fantastic shrouds, imagination, skill, craftsmanship demonstrated, only to end up a frisbee across the backyard .
Heartbreaking art .