I'm pulling the engine out today, 3.5 manual 2001.5 Path, I'm unable to locate the flywheel lock tool ie J-50288 Ring Gear Stopper. I'm concerned with keeping the engine from turning while working on it, and whilst the heads are off (bad head gasket)..is this something to be critical about or not? aside from removing the crank pulley which I'm confident I can do without the flywheel locking tool..any suggestions will be appreciated. I've relied on this site 90%, some others here and there for researching various issues w/ "fixing up a 2001.5 Pathfinder Manual 4x4 "..it started w/ learning the IACV wiped out the ECM, which has been repaired and since have replaced alot of parts etc. I'm an aircraft mechanic,(formerly regional commercial jets) BUT i'm learning the ins and out w/ these older "save'em or junk 'em cars",..the body and frame are solid and it's a manual with the metal valve covers and the front strut towers are soild too. I've had this for a year tackling and figuring out various quirks. It's a solid 4x4, has 154,000mi, juust needed a little TLC..finally a bad RH side head gasket. I removed the exhaust and it spits out coolant on the right side and the oil is a watery gas/coolant mix..I've previously, replaced the entire upper intake and gaskets/PCV, coil packs, valve cover coil seals, fuel injectors..down to the intake plenum researching into the power valves, BEFORE i learned from this site that the power valve issues are only on the auto tranys. After I complete the head gasket issue ..the rear bottoms out with the back end loaded w/ parts and stuff etc..ie last yr I replaced the front and rear suspension w/ " the cheapest" front coil overs and rear springs and shocks I could find, intended to use the Path as a daily driver in PA weather with light off-road use as needed..rockauto rear and online front coilovers ( at the time I was certain she was good for and insp sticker..aside from the steam coming out the exhaust whilst moving the car back and forth in the winter vs actually driving a few miles etc being certain it needed nothing else)..Now the motor is pulled out and I'm about the tear it apart..figuratively)..From this site I've learned the rear bottoming issue can be fixed by using OME rear springs..like i can see the bump stop inside the rear spring pressed against the rear end etc..my plans are to attach a small uhaul trailer w/ tools and misc when done, the smallest trailer come in at 900lbs, the Path already has a tow hitch installed, so I'm gonna need the rear susp. to be solid. My plans are to use the OME rear springs as they account for the ride height and possibly the Bilstein 5100's for rear shocks as from reading this site, any other brands simply arent robust enough and all are the same OEM issue of being too soft as this Path is intended as a daily driver light SUV...back to the start of this post,..as long as I'm CAREFUL to not turn to crank and move/turn the crankshaft etc when R/R the heads, do i really need the Ring Gear Stopper tool J-50288? as currently the tool is back ordered via the tool manufacture until MAY...
I appreciate any advice or direction...

I am aware of what the tool is used for but never thought it was important enough to me that I would want to spend the money on it. It's not critical that it is used, especially is you're just replacing head gaskets. I've rebuilt Nissan, VW, and BMW engines and never bothered with such a tool. If the crankshaft rotates a bit, for whatever reason, during your work on the engine, just rotate it back before you put things back together. Before you take things apart, rotate the crankshaft so that cylinder 1 is at TDC of its compression stroke. There are marks on the camshaft sprockets and crankshaft sprocket that line up with respective marks on the engine when #1 is at TDC of compression. That's all you have to worry about having lined up regarding engine rotation when you put it back together. The ring gear stopper tool might be a nice thing to have if you were a Nissan mechanic doing this kind of work frequently but I personally have done with out it and never had an issue.

kinda what I thought for a $130 tool..I've also scoured over the youtube vids and i refer to the FSM as well..Appreciate the advice! I pulled the motor as I'm also R/R the oil pan gaskets, main seals etc..the cats and all.