you can replace the primary and secondary chains/guides without pulling the engine in a quest. Recently did this in my driveway after watching the trurofm video on youtube…plus a bunch of other research.
The one thing I did need to do that he didn’t show (guessing due to the fact he worked on an altima) was I drilled a hole through the frame so i could slide the stud for the motor mount out. I couldn’t get that stud out any other way. Once that was out the timing cover could slide up and down freely. To make space to pull it out I also removed the thermostat and pulled the power steering reservoir to the side. I did NOT remove freon / ac lines…worked around those.