Hey, welcome to the forum
Ignor the modern haters, as I mentioned in a separate thread and in fact many times here, modern is not all bad and EPI is not half as bad as some will have us believe, but that debate may be for another day, or another thread at any rate
Anyway As for the poster I don't think it will be worth to much. Most poster values are held in One Sheets and UK Quads and the phantom menace posters aren't among the most valuable at the best of times. Posters like this will only appeal to a small number of people at best. From memory the final versions of these posters ended up as 25" x 35" posters and are bearly worth a pound or two, can't remember if they were promos with something or just sold in HMV and the like. Anyway as already said Evilbay is your best bet to sell but I wouldn't hold my breath - sorry, but mine is only an opinion so always worth researching further.