The best instructions for deck removal are likely in the operator manual. You can download one fromhttps://lookup3.toro.com/request/request.cfm
Use 78346 for a model number and 5912345 for a serial number. Not likely the same deck but the process is the same. Try your own numbers if you have them.
I use a 24" 1/2" drive bar with a socket to remove the nuts. Jamb the blade with a block of wood so it can't turn and give the wrench a quick jerk to break it loose. The long bar keeps your hands away from the blades in case something slips.