first of all - fitting a new radiator is not a reason not to fit an oil cooler. 2 different things. as far as i can tell-the external oil cooler works really well. how do i know? - well-my right leg doesnt get cooked when i drive in the summer. as for fitting- i bought an oil cooler for an equivalent of 30 $ - its a universal kit that comes with hoses etc. size? i went for the largest i could find- so its size is roughly the size of a shoebox lid.
now-fitting it is the tricky bit-you will have to fit it behind the front bumper and in front of the aircon radiator. how does it fit? the kit comes with these plastic rachet things that hold it in place in front of any radiator. and another thing-i fitted it behind the aircon fan. in order to do that i put some small spacers on the 3 bolts that hold the aircon fan in place-thus extending the fan about 1 cm forward. why? because now when i turn the aircon on the fan also cools my oil cooler. i will be glad to take some pics-but its in a really bad location behind the bumper. in total- 2 hours work. 30-40$ (i dont know the price in the USA) and it works.
p"s- dont forget that the main target of the cooler inside rad is to make your trans. oil heat up faster-so i guess if u live somewhere cold it does make some sense.