Crackeed Schrader Tube in air conditioning

I have a rental property and had an a/c guy come look at the cooling system as the tenant said she had it set on 69 but was running close to 75 degrees in the house.  He stated that the schrader tube where it was soldered and the refrigerant was running through was cracked and would need to be replaced. Would run me close to $989.  Any suggestions or other opinions on the price or how to handle? Is it serious enough to just replace the entire unit if it is around 15-18 years old? The square footage on the house is around 1350.  

Thanks!