I think the oil cooler was well worth it. When you mod an air cooled engine it's a good idea to add some extra cooling capacity. The most noticable difference it made was in the smoothness of shifting, reduction of clutch drag, and it seems like the oil lasts twice as long now too.
I put mine together with parts from the big bear, and a hayden 401 transmission cooler. It cost me about $100 for everything, mostly from ebay, and it bolts right on instead of having to remove the clutch cover, drill the oil galley, plug the channel between the holes you drill, then tap the holes and install the hose fittings. Then you gotta go through the pain in the ass process of scraping off the old clutch cover gasket, and installing the new one. With the big bear parts, all you do is take off your oil filter cover with 3 screws, replace it with the big bear parts, and then run your lines and mount the cooler.
The a-arms I have normally cost $450 (
www.burgardcycle.com) but I got a special deal on them because burgard is a local company, and works with the powersports shop I go to. I paid about 350 for them, with some custom made honda-style tie rods. I think they were well worth the money. Combined with the works shocks I got some more suspension travel, and the works shocks make much better use of it than the stock ones did. Yeah, they would fit the raptor 350 too.