How to change my avatar to black?

SWMBO has taken my avatar/logo to a local trophy shop to be etched on glasses. They are willing to deal with the pale green (which I call oasis green) but recommend that I convert it to black.

My attempts are failing. Any suggestions?

I've tried to change colors in both Photoshop and Paint, but end up with a splotchy mess.

The logo was made at http://www.says-it.com/seal/ but it now gives me a "Forbidden" message. So I cannot recreate it there.

I'm guessing I'm going to have to try to create a new version Photoshop, but I'm partial to the says-it version.

Have you tried to render the photo to black and white?

I'd offer to do it for you, but I'm out of town for the weekend. If its not a pressing issue and you can wait til Monday I'll be more than happy to do it.

No to rendering. I didn't see it as an option in either Photoshop or Paint. What's it under?

Back home I new layered it an saturated to a middling gray. I did not see the "Black & White" option.

As I'm not at the keys, I'm unsure of where to find it. I believe under the tab "image" there is a render option with a bunch of settings. One of them is b&w. Sorry I can't be more help as I don't have my computer with me.

While I couldn't get it darker than a middling gray in Photoshop, I did get it to a much darker hunter green in Microsoft Office Picture Manager. We'll see what the trophy shop thinks.

Gimp has a 'color to' option if I remember correctly. If it still needs tweaking it may be worth a look.

Here you go.

The way I did this was:
1) download the free scientific-image procesing program ImageJ
2) Convert to 8-bit (greyscale) image
3) Use the threshold feature to convert to true B&W.

Thanks y'all.
We have some options.