Hi Gern,
I was very similar to you, built a MAME machine, found my way into Pinball, and wanted one. My answer would be it depends on how technically proficient you are. My MAME machine was built using a cabinet kit, the PC works fine, but I've never put the finishing touches on it once it became playable. It's nice, but not perfect.

For me, I'm glad I got a working pin with no issues as my first. This let the pin bug bite me without frustration setting in. A few months after that I got one that needed help, and worked on it, but always had a working pin next to it which was a nice motivation. It was also a nice reference tool to have.

If your MAME machine is done and complex and slick, you're probably fine with the Lethal Weapon. If you're like me though and it works but is technically unfinished, you might want to keep looking.

Luck!