In the 49,000 or so miles I've had my Z, I've only had to replace the alternator at around 100,000. Timing belt at 120,000, and attempted to service AC, but it was going to be too costly <$400> considering I rarely use it. The brakes will need replaced again soon. The leather seats were so worned and scuffed when I got the car, I immediately had them redone for a reasonable price of $500. At around 85 or more MPH, there is a slight vibration from right front end. Overall, I've fortunately had to do very little in the many miles I've driven it.
First I like to say that if acceleration is one of your key reasons for wanting this car, remember that the non-turbo manual trans, kicks out 222 HP, while the auto trans reduces around 15 of those horses. Since I fell in love at 1st sight, I had to have it. However it ended up being a automatic. That sorrow only lasted a couple of days, however. If you drove a Z the first time and didn't know whether it was turbo or non-turbo, belive me, you still wouldn't know, until told. The non-turbo is just that quick.
All permormance mods I've done have been in the last 15,000 miles, which include: K&N cold intake <$40> which didn't give me the 15-20% more HP it promised, but still provided a noticeable change. You can easily add significent HP to your non-turbo, by aftermarket exhaust systems. I went with the Espalier exhaust <$80> and got a decent increase of power and for only around $80.
For appearance I added the rear spoiler-wing from the turbo model. Which adds to the aggressive look, quite well.
The seats were comfortable and snug. You'll love sitting in the cockpit. A minor complaint would be the distance to the stereo and other controls from sitting back comfortably. This car surprised me with its handling. Most sport cars in it's class are no where near the handling ability of the Z. I've never had the car over 120 mph, but have read they can get up to 180ish? My 1990 model was made with no back seats, but even if it did, the 300ZX is not a roomy car. However if you like good sound as myself. You have the room behind you to throw up to four more speakers and two 12 inch subs to top it off. The 1st thing is to get rid of the stock Bose system. Speakers and all. I went with a Clarion multi-colored head unit to match dash color <$375>. I have Polk Mono's 8 inch door speakers <$200 pair> that fit well on doors along with matching 3 inch tweeters. I went with Alpine 6X8's <$140-50> in rear. Along with the matching high end J L Audio's 12's <$400 each> in an enclosure, the whole car sounds crisp, loud and has plenty of boom-boom. Only complaint was having to install my amps so close together. After the subs, you have very little space left.
If there calling for snow, DO NOT drive your Z. But if the suns out and you have T-tops as my baby has, by all means take them out and enjoy the ride. This car is so fun to zoom around in, and attracts attention anywhere you go. Its so easy to get caught up in the acceleration. I recommend a radar detector if you put in a lot of hwy miles. The car is indeed quick, and oh so sporty, but it comes at a cost. Find a reliable and honest mechanic, and always have cash put away. For the average price of the 90 model these days <$4000-6000>, you cannot go wrong. Look to spend more money on fuel. Look to put out serious money for parts and labor. Also look forward to stares, questions, and attention from both genders. Leave behind a GT, Z28, and all those pocket-rocket wannabes. People can modify and add body-kits, etc, but with the Z, you can do the same and always have the power to back up that pimped out aggressive look!! Most importantly, it can all be done with great comfort and handling. One day, I swear, I'll have a turbo!!