Not to get into too much talk about 'hacked' exes but the 2.6 can just be dropped into the FP folder (name it as such if you'd like to keep it separate from your other exes).
As for dlls - you don't need to worry about them. All that the dlls from 2.5 provided was a smaller memory footprint, faster load times and less table crashing. The downside was that you could not see the images in the editor if and when you edited the tables. Personally I would stick with the old dlls (original).
P.S. - I have it on good authority (this info)