From what I hear, 15 years is the end of the expected lifespan on machines. Maybe they can be pushed a little farther, especially the dryers, but you should expect to need to do a complete re-tool and soon.
As to the cost, well, I’m also a newbie and beginner so I would really like the answer to this too. I’ve heard quotes ranging from $150,000 to $600,000, and I always find that wide of a range to be useless. Obviously the size and quantity of the machines and the brand make the difference, but what is more common? Can it be done for less? (Should it be done for less?) I don’t know. I’m looking at an older laundromat as well and I’m struggling to tell whether it’s worth retooling or not.