Change the boot $80 but don't forget your shaft maybe damaged already if your boot is cracked now.
If it is damaged now, even you change the boot, you might need to change the whole shaft again shortly.
As I know, change the whole shaft cost around $150 but for sure it can last for few year.
A lot of people leave it like this until the shaft need to replace. Sometime just change the boot is not worth it. You pay around $60 more, you get a new one.
Usually when the shaft need to replace, you will hear "clicking" noise when you make a sharp turn, like 90 degree angle.