Bunch of good stuff (used to be) on Youtube, things like jb welding cylinder ports and the like. There are forums out there with rich details on modding them. Before doing anything, spend some time with no mods, get to know what pellet it likes, and how well it does/doesn't shoot. I had one that was a turd from day one, and the next one was brilliant. No need to polish a turd, at best you'd have a turtle..
If you fall in love with it, set realistic expectations. Maybe you want 30 decent shots, maybe you want to shoot elephants for 10 shots. Pick one, and develope the rifle along that goal. It wont be an fx/Edgun/Daystate, but it can hang with them for 10-15 shots, with the right setup, pellet and practise. B Walton has some amazing videos of hunting with them at incredible distances. You may not be a B Walton, at least not at first, so allow yourself time to grow.