Your laptop specs sound ok I've got Linux on a much older one and it runs fine. Photoshop to my knowledge does not work with Linux (it might with wine but I don't use wine so I don't know) Linux has an excellent image manipulation program called Gimp. As far as dual booting, I'm assuming windows/Linux. I've always loaded windows first, resized the drive to create space, installed Linux then use Lilo as a boot manager. Never had any real problems with this method. Don't know the size of your hd but if it's in the 4g or more range you shouldn't have any problems.
Good luck.
