The Tokheim 300 was introduced in 1955. Your i.d. tag will have to month and year of production following the model number.
If I were you I would start by reading back as many questions and answers that have been posted here on this discussion form. Questions about removing or keeping the guts, painting, reproduction globe or original, etc., have been answered many times in the past few years. Then if you have any specific questions, you can post them here. If you are in need of any color seles literature, color ads or a parts/repair manual for the 300 I can supply them. You can contact me at: jhsim@swbell.net. You might also want to take a look at my gas pump website:
www.crspub.com Jack Sim