I read Starship Sakira last night and was reminded of a book I read in 2014 that matches the genre. It was about an older man that finds a sentient star or space ship buried in a gold mine in Arizona. The ship ended up buried in the earth due to a warp accident. The main character uses technologies found on the ship to mine local gold to create startup capital to create his own company dealing with flying cars and space capable craft. Also uses nanotechnology from the ship to rejuvenate himself and older/disabled US veterans to have bodies of mid 20 year olds, but the ship makes them keep their old looking faces for biometric ID, worried that the government would freak out. That's about all I can remember.
This is the book Gray Panthers: Battle for Earth by David Guenther.
It is set in a somewhat dystopian near future USA and the protagonist is Danny "D2" Daniels. He finds an old gold mine and exploring it finds the spaceship, which is called Grub. The scene where the spaceship rejuvenates Danny is:
"I analyzed the contents of your pockets as part of an anthropological study of your society and your position in it. Now be calm and the side effects will wear off soon. Your heart muscle was going to fail you. I can reverse the repairs I performed on you if you have any objections. I have no wish to alienate you."
Taking a deep breath and feeling his lungs fully fill like he could not remember when, he calmly replied, "I will forgive you this time Grub, but in the future ask first. How long will your repairs on me last?"
"The nanites I implanted in you are self regenerating so any damages they fixed will stay fixed as well as any new damages will be repaired. Unless I have them removed from you, you will stay healthy forever."
And as you say Grub leaves Danny's face unchanged.
His first reaction was one of disappointment as he saw his wrinkled sun burned face covered by his scraggly gray beard. Opening his mouth, he noticed his partial denture was gone and that all his teeth were once again there, not a sign of rot or cavities. "Hey Grub, great dental work but isn't there something missing with the rest of my head?"
"Appearance was not a concern when the nanites were first created. The important requirements were that you were healthy, mobile, and capable of quick aggressive action when needed. It was decided to not make any changes to your face so you could always be recognized and not use the nanites to hide from any authorities, the only exception was when repairing the face."
Found by Googling for spaceship gold mine arizona site:goodreads.com/book/.