How deep is your sewer line? This can be very dangerous work if over about four feet deep. Not recommended for amatuers. If shallower than that you may have a go at it just be extremely careful of cave ins. The only way to replace the line with open cut methods is to cut the street if you need to go all the way to the main. There are some pipe rehabilitation methods where a liner can be installed without digging up the whole line but is definately a specialized field only for professionals with proper equipment and knowledge. Not familiar with pricing for those methods but I would doubt it would be cost effective for a 30' residential sewer. As far as if your responsibility ends at the property line or the main would be up to your local sewer district as rules vary fom municipality to municipality.