One of the purposes of C1 is to help damp-out input voltage overshoot. The 50 to 100m cable has a lot of series inductance. If you were to put, for example, a 10uF ceramic cap in place of C1 you will probably have a very large voltage overshoot when you first connect the regulator. Very possible to blow up the regulator first time you plug it in.
I do not know if 1000uF is needed. But if you make any changes, make sure you test for overshoot. Electrolytic caps generally don't overshoot as much as ceramic because their effective series resistance provides damping. It is also possible to add a resistor in series with a ceramic cap to get the same effect (but you may have trouble finding a 1000uF ceramic cap!). Also, if you add a fuse or PTC to the circuit, that may provide some damping. The amount of resistance needed for damping may less than an Ohm. Simulation can be done if you have very accurate models. Otherwise you can test it and monitor the overshoot with an oscilloscope.
Application Note 88 by Goran Perica of Linear Technology goes into a lot of detail about input voltage overshoot.