In the event you plan to proceed you should get at least 4-6 more estimates on something of this magnitude. Need to consider options such as directional drilling contractors that can offer some options and minimize impact as part of their work.
Assuming your sewer camera footage shows you the lines of most concern would be worth considering if you can perform the upgrade in a phased manner instead of big bang (e.g. absorb as part of operations instead of coming out of pocket).
If the economics won’t support it then walk.