I was just looking for internal pics of a GR-213 recently, so thanks for posting these.
I have a small external antenna that came with a Holux CF GPS, and I was thinking I'd hack this onto the GR-213 so I could hide it under the dash somewhere and just have this small antenna in the corner of the dash. I could either install a jack, probably rip the one out of the dead CF unit, or just solder the coax of the external antenna directly onto the GR-213.
It's kind of hard to tell from the pics, but is the big chunk of metal in the left pic the antenna? Does it connect to the board with the big gray wire on the left side of the board as shown in the right pic?