The COL doesnt really matter in a single shot, it does matter very much in a repeater with a mechanism that can hang up on a too long cartridge. Depending on the throat of your chamber it may be able to take longer than repeater spec COL to get the bullet up to the rifling, but that is an often over-rated 'need'. Reloading for now you will seat the bullet to the crimp groove on the bullet you get and forget about that COL thing.
You already have some brass
Get the dies and a press (I have used the reasonably priced LEE products for years with very few problems). The LEE die sets come with a powder scoop and a Shell Holder. A note on presses: the single station bench mount 'basic' press will be fine, or even the LEE Hand Press (I have two of those too along with my bench mounted, just plain handy to have and you can reload in the livingroom or kitchen).
Get the LEE 'Case Length Gauge' and cutter tool to easily trim all those case to length as needed. It is the quickest and easiest trim tool out there.
Get a jug of Trail Boss Powder; you can load this from 'powderpuff' to top trapdoor loads without worries.
Source some cast bullets (someone here can suggest where, Im sure) in probably .459-.460 dia.; you can get the LEE 405 gr. Bullet Mould now or later, but you will likely get one eventually.
Get a box of 1000 Large Rifle (Std.) Primers
And a Priming Tool (again LEE has a couple of choices).
OK, now you are going 'gulp'......thats going to cost some serious change! Well, how much does each one of those boxes of 20 cost you? This stuff will pay for itself in about the first 100 rounds you reload and amortize down after that. It is, by far, the cheapest way to shoot that you can do, even if you decide to buy expensive jacketed bullets instead of lead.
Look this stuff up online (LEE has a site and Midway, among others, is good). Check the stuff out, even compare my suggestions to other brands and ask a few more questions here; remember, we're pullin' for ya