Here's a download:
ParkDat.zip
It's kind of hard to explain how it works but here's a quick summary:
Click the '...' button to browse for the park. Once you've found it click Open and it will load the parks DAT items.
To insert an object you can either Add it in an empty slot or Replace it with an object that hasn't been used in the park. You can see if it's been used by checking for an X and it has to be the same Slot Type (Small Scenery, Large Scenery, Walls, Rides etc.)
Then click Save and you're finished.