A few years ago I had a great experience with T&T Engraving in Colorado Springs.

Call us: 719-632-2780
2605 E Willamette Ave., Colorado Springs CO 80909
tt.engraving@prodigy.net

At that time the same location also housed "Deep Discount Gun Broker"
It is always a good idea to have licensed individual handling your firearms, especially when they are being "worked on"

Because I was in contact with them before hand and set up a day / time to come in they did the engraving while I waited.
I provided a copy of the ATF instruction that describes the size, depth and font required for the markings.
They may still have that sheet.
The approved FORM 1 showed exactly what needed to be engraved on the receiver.
As to the "where" its engraved, the guidance just said it has to be readily visible on the firearm.

T&T did what was required, was fast, did a great job and charged a fair price.

Richard