Hey,
With a little shock like that, 1L will make you a bath in a suitable container which will make the whole process much easier. I'd start by making sure you have a suitable setup available to repressurise it (a fitting or shop or whatever). Then remove the spring, clean the shock up really nicely and just unscrew it... pull out any seals that you think are leaking and get them matched. Most shocks just use an o-ring to seal the shaft with a wiper on the outside (that looks like a pressure seal but afaik doesn't act like one) so that's usually an easy replacement, but most seal shops will match the pressure seals anyway. You can usually remove the ressy cap and pump the shock with oil still in there to make the IFP (floating piston) fall out, which you'll want to do first.
For oil, just make sure you get something with a high VI (shock specific oils are good, or silkolene pro RSF is great). Normal fork oils aren't great although they'll still work if you're tight / don't really care. I'd start with 5wt.
Then just build the sucker under oil, I'm not sure if the seal head for the shaft comes out but it'll be a pain if it doesn't... generally I just remove that and the ressy cap (perhaps circlip'd in on that shock?)... get everything filled with oil, and then push the IFP in (3/4 of total depth is a good estimate on most shocks), then install the seal head. All under oil. If the IFP has a bleed screw on it you can swap the order of those steps but most cheapies don't. Then recap the ressy, repressurise (150psi would be my suggestion to start with), clean it up, and off you go.
Probably repeated heaps of stuff you already know but I have no idea how much that is.
