OP, consider also that your '91 Maxima is acting JUST like a '90's Z32 will act without the kind of maintenance mentioned above, and more. 20-year old cars all have a tendency to be unreliable unless it's been maintained in a really consistent way, end even then things do tend to wear out just from time or other issues such as electrolysis and heat.
I bought my current Z in SF and drove it back, not a hitch or anything wrong with it but immediately I went in and replaced the entire fuel delivery system, vacuum hoses, and replaced the injector connectors and several other connectors along the way that were corroded or broken or both. Almost every connector in the engine bay needs to be inspected and cleaned/replaced even in a really clean Z. Then came new tires which are easily in the $1,500 to $2,000 range for 18" ZR speed rated tires, a battery, and a complete fluid service to the car. All done just as Afi wrote, simply for piece of mind and knowledge these areas would not be problems in the future.
Now, two years later a turbo is down and several other areas of the car all at once as well, all beyond my means at this time and so off to my Z guy it goes for $3,500 in service costs. I paid $1,200 for new turbos and downpipes, and +/- $300 for clutch and rear main seal. My '93 also has the earlier injectors that fail from ethanol and electrolysis, a $700-$1,200 cost for the future that WILL come.
I've also had to replace the intake hard pipes with silicone pipes, replace the PVC's and hoses, and fix several other small issues which have totaled about $1K cost- so, you HAVE been warned both by your current car, and all of us about what you will be undertaking.
BTW, I say this having been EXACTLY where you are when I was your age, a '67 big block fastback Mustang was in my sights. My Dad did exactly as your Dad did, and I bought the heap from some drug dealer it turned out and I forever learned a valuable lesson as it just killed me financially and rarely ran right. I later bought a nice '67 GTA big block fastback that had none of the problems of that first car, but a FAR steeper price tag and it eventually had to have a new motor as well. I blew about $5K on a 600+ HP build that I did myself and never really came out right completely, and it was sold off to some lucky stiff for the money I had into it (and even then only because I had some really rare parts)...so realize that we have all been there, done that, and we are FAR from the first to have done so...
