I doubt there would be as much of a "spray" of brake fluid, but there will definitely be a lot fluid spilling/flowing out of the caliper after you eject the piston.
I had to replace the seals & boots on a stuck piston on the caliper of one of my cars, thankfully I do have compressed air but using the braking system might have been more gentle (using 90-120PSI to break a piston loose isn't fun at all).
You will need a couple of C-clamps and a piece of wood or something to hold 3 of the 4 pistons in place. You will then use the brake lever to eject 1 piston at a time to replace the seals. The pistons (at least in my car) aren't nearly as long as you would think but you will need to be careful with the positioning of the clamps/wood to hold the other pistons.
As Grn14 mentioned, bleed BOTH calipers first, if you see bubbles of air coming out, see if that fixes the problem first. As for which seals, the ones with little to no wear are the ones with the problem since they aren't pushing against the rotors and the other pads that are working are doing all of the work. On my car the inside pads were at 80% and the outside pads were down to 5%, the inside pistons were seized and needed to be fixed.
If it is the seals, it was actually really easy to replace the seals and dust boots (don't think the bike has dust boots now that I think of it). Pull off the old dust seal (if there is one) then pull off the old seal out of the groove, put the new seal in (use some clean brake fluid to lube the seal), make sure the caliper bore is CLEAN and free of defects (cuts, bumps, etc) press the piston with the new seal back in, then press the dust boot in making sure it fully seats. After you've done all of the pistons, bleed the system.
A couple of things that should be obvious but just in case, wear safety glasses!! remove the brake pads, dismount the caliper, but don't let it hang by the hose (use a piece of wire to hold it), cover the rotors and anything you don't want brake fluid on.