Tires: Tire situation, rear tires, allignment

Question
Hello Barry,
I read through your answer to my previuos question about the tires. yes, I'm the same person with the weak rear tire. I took the car to one of the tire mechanics here who told me that once before when i got a puncture repaired on one of the tire in the back (the trouble maker). it seems the same puncture is the problem again and the leak s quite evident. The new mechanic told me that it can't be repaired and that I ought to replace the tire with the same make and owing to the less mileage I could change one of the rear tires to the same brand and spec. Thus solving my issue.
I am contemplating on taking his advice on this, but the uber price on these tires can cause a crater in my pocket.
assuming I replace that single tire with a new one with the same brand specs tire. Is there anything i need to be warned about and is there anything i need to remind the mechanic during installation. I also would like to do an allignment - should I do it on all 4 tires or just this one?
Appreciate your help on this one. I understand that I'm being too bothersome with so many questions. I apologise for the inconvineance.

regards,
John Simon

Answer
John,

If you replace that single tire with exactly the same tire, then unless there is considerable wear on its mate, then that would minimize any risk.

Alignment is not just a single tire type of thing - you can only do the whole vehicle.

But other than that, there isn't anything more you need to tell the mechanic.