Your best bet is to contact a local septic installer. There is the cost that John outlined but there are some costs and steps that may need to be taken to abandon the old septic.
You also want to check with the town about monthly or quarterly costs for sewer/ water bills and the betterment fee.
there are 2 parts to this
1st) there is typically a "betterment" which is essentially a fee the town charges to each home for the privilege of the sewer coming by your house. If sewer has been there for years this may no longer apply.
2nd) there is the connection fee (bringing the line from the street into your home) which is what the town approved contractors will do.
These contractors will typically bid the job by how many feet your home is from the street and any obstacles along the way.
I hope tis is helpful. best to call the dpw for more info