I dont know what the square foot rate is where you are. I usually estimate based on the time it will take anyway. So, you have 1 day 'worth' of cleaning, then have to wait a day for drying. Use an 18" roller set up for staining. That's 1 day. 18" roller for sealing is 1 day or 2 if more than 1 coat. Then throw in your hourly rate. I'd say (just for labor) between $1000-$2000. Depending on your rate and other factors, such as how dirty it is to clean and such....
Note: this is only an estimate based on my own criteria