[Efini]

So I hit 70k miles on my 07 328 and the car has been running well so I wanna keep it that way. Should I start with preventive maintenance with these miles? The car is a dd, I drive around 40-50miles a day. Looking for some serious responses from locals. Done plenty of research on the forums and everyone has different opinions but looking for some good replies from this cali section. As of late I put in a new belt tensioner, battery, and coolant. Oil changes on point since day 1. I already purchased diff fluid, should I drain and refill diff fluid?? Is it a good idea at 70k??? Should I get ready for plugs? Solenoids? Any recommendations please.

Current problem:my car is having the steering column lock issue. It does it every now and then and I'm pretty sure it's gonna leave me stranded sooner or later. Stupid thing is getting stuck and saying my wheel is locked when it isn't. I am a diy guy and say the posting but was wondering about that that 5 point security key. I don't think I have that. Ant pictures of what it looks like. That's the only think keeping me front fixing the issue this week. What will a shop like ltmw charge to fix the problem?