Engine light on, codes P0691 and p068b

P0691 relates to the cooling fans not being powered either through a bad relay or blown fuse.
P068B is a code that shows the power relay that sends power to the ECU/PCM is not shutting off properly and could damage the ECU/PCM.

The ECM main power relay is a somewhat known issue on these and could be the cause of both issues. It provides the ECM with power and it also powers the fan systems. It is also possible it is an internal ECM problem.
If it is only the relay the pricing would likely be under $100.00. However if the ECM is damaged it could be much more. Without testing to verify what is wrong it is very difficult to give a price.
It also depends greatly on the shop you take it to. If they are a shop that believes in testing first to find the failure and then repairing that or if they just keep changing parts out until they find the one causing the failure. The latter will cost you much more overall as you will pay for each part they swap, even if it does not work.