when looking up brake pads...do I get pads that are for the Sport or base. I would assume base right?

yup they should be the base pads, best way is to look at your front calipers and if they are one big piston (u see one big half circle vut in the middle of the caliper like THIS(not G)) you have sports, but if you have 2 pistons then you have base(two half circle cutouts on the face of the caliper like THESE)

Would a DIY for brakes for a 2003 G35 be the same for a 2008...both being non sport ones.

brake pad changes are the same on most cars, the DIY should work fine except that some bolt sizes or the bolt type might be different but same procedure should work fine