We present a time-resolved pump-probe low energy electron diffraction experiment to study the dynamics of surface phase transitions. An ultrashort laser pulse heats a surface on a picosecond time scale, and a time-delayed, photogenerated electron pulse probes the resultant surface dynamics by diffraction. The diffracted electrons are detected with a position-sensitive microchannel plate detector. We discuss the limits of the achievable time resolution as given by the time-dependent surface temperature jump and the temporal broadening of the electron pulse due to the kinetic energy distribution of the electrons, the focusing of the electron beam, and other effects. The instrument function of the experiment, obtained by monitoring integer- order diffraction spot intensities as a function of surface temperature (the Debye-Waller effect), may yield the electron pulse duration. A model for the surface temperature profile based on a solution to the heat conduction equation, and a simulation of the electron trajectories in the electron gun, show that the instrument function is on a picosecond time scale. Initial experiments focus on the dynamics of reconstruction on the clean, single-crystal W(001) surface.