You do not necessarily need the OEM tool - just use a square drive screw mounted (screwed) into a block of wood. Use one long enough (2-1/2") and put a little glue on the end so it won't back out.
Also.... be very careful about the alignment dowels found on opposite corners of the valve cover. THEY CAN FALL OUT AND GO INSIDE THE ENGINE RUINING YOUR DAY. They will likely stay in either the cover or the head but make sure you're aware of them and be careful.
Also, try to leave the valve cover gasket on the head - it will likely try to come off with the cover but if you leave the half-moon part of the gasket in the head you won't need to reseal that part. Watch the little o-ring gaskets on the oil lines too. They can pop off and get lost easily. I usually put a zip-lock bag over the end of each line to keep dirt our and keep the o-ring in place. A small ballon works works well too.
Take your time and take pictures of the engine before tearing things apart - that way you know which hose, cable, line, etc. goes over which. I try to set the clearance to the middle of the range using a go/no-go set up of three feeler gauges. Middle one should go - the thickest one should not. Clean all gasket surfaces really well before reassembly to avoid leaks or weeping. Wipe/clean all fasteners of oil and BE SURE TO USE A TORQUE WRENCH to tighten things up.
Tools that will come in handy will be a socket wrench extension (3" long), an 18mm spark plug socket, a hex head socket that is modified to be 1-3/8" long overall (pound out the hex and cut or grind to length - reinsert), an 8mm combination wrench, 19mm & 10mm sockets and a rubber mallet.
Hope this helps.... I just finished doing mine and it always feel better knowing it was actually done and done properly.