RE: How many miles can you get out of a 2000 dodge neon...
Keep up with or ahead of the maintenance schedule in the owner's manual/FSM. Timing belt, water pump, and tensioner parts should be done before you get to the recommended 105k miles.
When you get a CEL, find out what it is and fix it.
You can't change the oil too often. A good synthetic goes a long ways, so does a quality filter.
Check your spark plugs every oil change and replace (as a group) as necessary. I normally do mine every other oil change, but that's probably overkill even at $1.00 per plug (Bosch coppers). Copper plugs are fine.
Replace the cooling system twice a year. Spend the extra on the premixed coolant. Don't ever put tap water (mineral deposits) or DI water (corrosion) in your car. Demineralized is fine, but I stick with the premix.
Avoid additives. Avoid gimmicks.
When the suspension goes, it's typically cheaper to upgrade than to replace with stock parts. Same goes for virtually every component on the car.
Spend the money on a lifetime alignment from Firestone ($160 or so). Use it a few times and it pays for itself. I've used it 9 times in less than 2 years. My 160 treadwear summer tires have lasted almost 37,000 miles now with 80% tread remaining because of proper alignment and frequent rotation/balancing (also lifetime - mounted at Wal-Mart for $40).
All-seasons are not. When you can afford it, get quality summer tires and quality snow tires on seperate (i.e. steelie) rims. I live in Albuqerque and still use snow tires every now and then.