Actually, it does. L*a*b* is what's known as a vision color space, or perhaps a profile connection space; because unlike RGB or CMYK, L*a*b* is not device dependent. And while there are some other PCS spaces out there, L*a*b* is by far and away the most commonly used one these days. So it'd be a smart wager that behind the scenes, your RIP is using L*a*b* as its own PCS.
So what's the problem?
Lab colors. I have no idea what to do with them, and neither does the rip...
The trick is getting all your procedures in place, and setting up a workflow that integrates them all correctly. These guys have put you on the right track, but it doesn't look like you're there yet.
What you asked for in your original post, for someone to come in and help...well, that is what I do for a living. If I can help, please drop me a line at email@example.com.