Welcome!  Firstly the BB will be 68x128 most likely and I'm assuming square taper with it being Onza's budget bike (the general standard for trials is splined even though the rest of the bike world ditched it years ago!).  If I'm honest I wouldn't bother upgrading the brakes, a well setup set of V's with decent pads (check out Tartybikes for a good selection) will be just as good as maguras and they tend to be a bit poorer when fitted with adapters for V mounts anyhow.  Best practice would be to get the basics drilled and if you're sure you want to stick with it sell the bike and buy something with a better spec.  The Onza Rip was always a budget beginners bike, no hydraulic brake mounts and a 20" rear wheel instead of the standard 19" so not really much point in spending too much on it other than to keep it rolling smoothly.  If you decide to stick with a mod (20) then go for something with magura and/or disc mounts and a 19" rear wheel. Otherwise there's the 24" market (predominantly street trials based) or 26" (street trials or high BB seatless bikes) to move to. 

I've seen a load of auctions recently that were selling, ended then somehow are relisted and I can only assume it's people playing silly buggers not getting what they wanted. I'm yet to be stung myself but it's defininitely a dick move.

https://www.instagram.com/tv/CNfmotopo_j/?igshid=1mwk10ujidy80

f**king sellers on ebay, just won a pair of wheels, tyres, disc rotors and cassette for £130 which were for one of my sons bikes. Paid instantly on PayPal then saw a message saying not to as his account wasn't working so I cancelled the purchase. Only realised now that he didn't get what he wanted for the wheels so came up with a bullshit excuse to get me to cancel it. Cünt

I’ve been considering one of these for quite a while, been waiting to jump on any that come on sale. The black one looks great but they’re not easily available in Canada unfortunately. Any tips or considerations you’ve learnt from your machine?