Finding Gibbs energy at different temperatures
You might know that Gibbs free energy is given as:

$$\Delta G=\Delta H-T\Delta S$$

This implies that:

$$\Delta G^\circ=\Delta H^\circ - T \Delta S^\circ$$

Which can be rewritten as:

$$\Delta S^\circ = \frac{\Delta H^\circ - \Delta G^\circ}{T}$$

Often it is a good approximation to assume that $\Delta H$ and $\Delta S$ are temperature independent. Now that you have found the entropy you can calculate Gibbs free energy at different temperatures using the first equation.

If you want to find the equilibrium constants, you might have seen this equation before:

$$\Delta G=-RT\ln\left( K_\text{eq} \right)$$