[bell]

The reason turning backwards is bad is the tensioners are on the "unloaded" side of the chain.....so when the crank turns backward it compresses the tensioner before the cam moves....making the cam out of time...basically....

Any time you remove anything related to the timing chains/tensioners you must lock the crank and the respected bank of cams.

I personally have installed roughly 40+ LN bearings on boxsters and 996s......you must follow the procedure....

Pulling the cams isn't a big deal, as long as you have the tools to retime...
and it's easier to do in a 996 than a boxster with the engine installed...