No I have not had the head resurfaced. Should it be done in a shop with a professional grinding machine? Or is it something I can do myself?
18 - 20 ft lbs is not much?
Ricky.... 18 to 20 foot pounds is a bunch and it is "On Target!"
On a flat surface, you can initially use a sheet of 320 wet/dry sandpaper... wet it down with mineral spirits, then run the cylinder head over it a few times in a figure 8 pattern. That'll show up any high/low areas. Finish up with a sheet of wet/dry 400 w/mineral spirits.
If you have a flat edge tool (metal carpenters square), you can check for wear, warps, etc by laying the edge on the head in various areas. Any light showing through would indicate a imperfection.
Machine shop work is risky but also perfect.... the risk is taking off too much, increasing the compression to a point that may result in pre-detonation which would melt a piston.