Would the Japanese recognize Warspite before opening the battle?

Would the Japanese still attack at Savo Island if Warspite were present?

In this scenario they would probably begin the attack without knowing she was there, then face the difficulty of withdrawing after her guns opened fire.

The counterfactual gives Warspite only a day to appear in the Allied force before the Japanese attack. The Japanese are therefore assumed to have little warning that a battleship has replaced a cruiser. Darkness further delays recognition, potentially until Warspite opens fire. An attempt to withdraw at that point would begin after the heavy guns had entered the action.