If you take out the upper bracket, sliding it back in place with a pole either wedged or taped on the end works fine as described above.

The 2 blocks on the upper bracket are just turning blocks, all the line ties are on loose floating blocks. if the lines are not broken, you can just feed new lines through the sytem, by tapeing the new line to end of the old and pulling through, retie at the end and replace the base. You can even replace the line that comes out through the mast without removing the base if you fish the block out through the hole in the base plate. To get both you have to take off the base.

M