No there are no numbered markers. I had to request the burial grid at the Minnesota Historical society and then pour over it to find my uncle's name (it was broken down by year, so not too difficult). I also made a point to note some of the people buried around him. With uncanny luck, the row he's in actually had some headstones set for the very names I listed. I was able to pinpoint his gravesite (within a foot or two) that way. By the time I get his headstone set it MAY be one of the most completed rows in the cemetery.
I actually made a photocopy of part of the burial grid. It's a four sheet composite it's so big. However, it's of Cemetery 2, which doesn't help you. The three cemeteries are side by side, and it's basically a mown grass meadow with a few standing headstones, a bird bath/feeder type object, a scattering of flat memorial stones, a cross and a flag on a flag pole (which makes it easier to see the cemetery at a distance). It's a little difficult to find the place. If we want directions I'll email them to you directly.
You may want to try to make a copy of that cemetery grid and see if there are other markers nearby to help you find your great-great-grandfather. Do you live near St Paul and the MN Historical Society? Otherwise, maybe Otter Tail County Historical Society has access to the same map.
Do you plan to take a tour of the abandoned Kirkbride hospital building? It's very interesting. They're trying to find a buyer for the main building and the whole hospital, if not, it'll be torn down. Most unfortunate if that happens.