We have a Morigeau-Lepine convertable crib-day bed-full size bed, but we are missing the instructions to convert it to the full-size. It's model number is DA722-BC & the model is somewhere between...
I can't offer the exact answer, but hopefully my suggestions will be helpful...
Converting the crib to a full-size bed should actually be a fairly simple process of detaching the 4 sides that make the crib, and replacing the 2 short sides with the full-size bed rails that were sold separately in a conversion kit. The 2 long sides of the crib become the headboard and footboard of the full-size bed.
Unfortunately, it's only a simple process if you already have the full-size conversion kit bed rails. And since Morigeau-Lepine went out of business, they aren't making any more conversion kits. If you don't have the full-size bed rails, then this could be quite difficult.
It's possible that some stores that used to sell Morigeau-Lepine cribs might still have a conversion kit hidden somewhere in the back of their stock room or warehouse. You could try calling around to a few of your local stores to ask if they would check for you. It's a long shot, but it doesn't hurt to ask.
If you have the rails, or are lucky enough to find them, then it should be as simple as locating the screws that hold the crib sides together, removing them (most likely with an appropriatly sized hex-key,) and putting the screws back through the headboard and footboard into the bed rails. (I'm really just assuming that it works the same as the Babi Italia conversion.) If no screws are visible, or if removing them doesn't detach the crib sides, then they are probably also held together with locking bed rail fasteners. To release the fasteners, remove any visible screws, then push upwards on the short side rail while pushing down on the long side rail. You might have to tap the rail up with a rubber mallot to get it moving.
If you don't have the full-size bed rails, and you can't find them anywhere, your only option may be to build them yourself, or find a woodworker to build them for you. Search online for "Bed Rail Fasteners" and you'll see several options for hardware, but they might require modifying the headboard and footboard as well. Full-size matresses are 75 inches long, so you'll want the length of your rails to accomodate (ours are 77 inches long.)
I hope I've been helpful. Good luck!