[davn]

you might want to take off the tailgate if you have any concerns at all, they actually come off so easy its scarey.

from the manual

Removing the Tailgate

To remove the tailgate:
1. With the tailgate fully open, lift up slightly on the
entire tailgate assembly.
2. Remove the retaining
cables from both sides
of the tailgate by
pulling the clips away
from the bolt heads
while pushing the cable
bracket forward. When
the larger part of the
hole on the bracket is
over the bolt, slide the
bracket off of the bolt.
3. With the tailgate partially down, lift up on the
passenger side and pull the tailgate toward you,
then move the tailgate to the right to release the
driver side. You can then remove the entire tailgate
assembly.
Reverse the procedure to reinstall the tailgate. Make
sure it is secure.

 

[davn]

Then you could add support under the boards your using as a ramp, be it cinder blocks, firewood, or wedge a couple 2x4's under there like "studs". If you can do this without sitting on the machine that would be a big help too.