The dealer has a Deere specific kit and is custom for your tractor. If you decide you want to utilize the OEM deere part, I don't recommend adding as you go. When you order the entire top n tilt kit, you pay a lot less than ordering individual components. I went through this some time back and with the assistance of a patient JD parts guy, decided that if the side cylinder is somewhere in your future, it would make a lot more sense to order the kit now and keep the rest of the parts for use later. In fact, just the top cyl alone was something like $500 (I might remember incorrectly) and the entire Top n tilt kit for your tractor is about $800 plus change. This includes the top and side cylinder, the cylinder ends, the angled clevis to attach to lower lift arm, all the fittings, the hoses, the replacement top link support bracket. BTW, you can not price the kit online as the part# will show up as invalid part #. I believe all of the John Deere kits need to be ordered at the dealer because they are probably designed and intended as options and upgrades through sales dept and not parts dept. You'll probably need to find a parts guy who knows where to look. Don't be discouraged if he says he can't find that part in his system ... it's there. You'll just need to find someone else who knows where to find it.
I recently performed some upgrades to my tractor: Installed Deere canopy, installed wheel weights, installed cruise control option, installed power beyond kit, installed DIVERTER valve kit AND finally installed the top and tilt kit. Took me a little less than a week to do everything on/off but someone working on it all day could probably have finished it in 2. I debated the cost to bring tractor in to dealer to install but decided that I would do it myself. I don't regret it one bit and I'll post the entire install in a few days, if I don't get too busy in other matters. You may want to watch for it if you are curious insofar as what is involved in the installation, especially with respect to the Diverter Kit, which is the most involved installation of them all.
I already had the 3rd SCV option so I can't provide any experience info on that installation, but I can tell you that you will need to remove the right rear wheel, the right control console pod, the right rear fender. At least the hydraulic ports are the easiest of the bunch to access on the dual SCV as they are the two outermost pair (out of the 6) of ports on the valve. You'll also need to make a cutout for the lever and the best tool will be a dremel with small cutoff wheel.
The attached image is contents of the Deere top n tilt kit (ignore impact wrench) I might have missed something else, I don't recall. I'm sure I could have been able to peice the kit together using non-deere parts and saved a few bucks but some of the parts are not available aftermarket and frankly, I prefer a complete kit, with instructions, designed and intended for my tractor and I'm rather lazy and knowing myself, I probably would have bought the wrong parts, and ended up with a bunch of non-used wrong parts left over and... oh what the heck, it's way easier and I'm darn lazy.