PCV maintenance questions

[big dawg]

I'm just trying to do general maintenance on my '90 NA 300zx and saw a post that said one should be regularly changing the PVC valves to avoid oil blow by at the cylinders or the rear main seal. I have 175,000 miles on my Z and have never had them replaced to the best of my knowledge. How do you know if they are in need of replacement?And has anyone actually replaced them while the motor is still in the engine bay? Looking at them, it appears to be a rather daunting task to get by all the hoses and wires on the passenger side and the large wire bundle and hoses on the drivers side just to have a shot at removing them. I saw a writeup in another forum on how to do this, but it was on a TT. Any tips on how to do this with the least amount of removal and what specific tools will be necessary to get them out?