You need to pull the steering lock fuse before it happens again. Even the replacement you got will still fail eventually. You need to pull the fuse before it breaks again, because once it fails again pulling the fuse wont do anything. Pulling the fuse only works with a working unit so you would then have to pay for another replacement and THEN pull the fuse. It takes 5 minutes, and you wont even get your office clothes dirty. See the DIY in southark's signature.
The soft clutch is probably from boiled fluid. You should bleed and replace the fluid with high temp stuff like motul rbf600 or if you just want to pick something up at autozone valvoline synthetic dot3/dot4 isnt bad. Good fluid also wouldn't hurt in regards to the life of your csc.
The csc's in these cars are garbage. It WILL fail eventually. It may fail at 100 miles on the car, or at 100k miles, but it is a matter of when, not if. The CSC is around the input shaft of the transmission on these cars, so when it fails it requires dropping the transmission which is labor intensive ($$$). My best advice to you is keep some extra money around for when it fails if you do not want to go ahead and address the issue now before you get left stranded somewhere.
When it does fail, you should under no circumstance put an OEM replacement in the car. At the very least you should replace it with Zspeeds HD (heavy duty) slave. But there are 2 other options I highly recommend. The first is the Zspeed CMAK kit. This kit comes with the Zspeed HD slave, but it moves the slave outside the transmission bell housing and uses a fork that reaches into the bell housing to actuate the clutch, similar to late model fords. aka, this means that if the slave ever fails again, you can replace it without having to drop the transmission. Z1 motorsports also makes a csc elimination kit, which is similar in function to the cmak kit, but it requires minor adjustments over time as the clutch wears. The cmak is set it and forget it.
Zspeed CMAK kit :
ZSpeed Performance Nissan 300ZX 350Z 370Z Infiniti G35 G37 Q50 Q60
Z1 csc elim kit:
https://www.z1motorsports.com/z1-pro...it-p-7340.html
Zspeed HD slave on its own if you don't get one of the above kits:
ZSpeed Performance Replacment HD Clutch CSC Heavy Duty Slave Cylinder Kit
If you look in the vendor classifieds section of this forum you may be able to get a little discount, but I'm not sure.
Also here is a sticky on steering lock failures:
Sticky***** Steering Lock Failure Database ***** Sticky
And a sticky on CSC failures:
Sticky: (Official) 370Z Clutch Pressure (CSC) Failures