Was about to buy an 90 Miata, but water pump just recently went off. It comes with a hardtop and i think its cheap. To get to the main question:
Will replacing the water pump be reliable in the future. (Dont want to deal with that in the future, if I do get the job.)

A Reply would be greatly appreciated!

 

If the work is done correctly, it should last as long as the first one. How many miles on the car and has it had the timing belt changed? If over 80K on the belt, you should do it at the same time.

 

Watch for wobble in the crank pulley on those early 1.6 cars.