There are a lot of variables here. First, who really owns the mainline sewer? You say the resort, but that may not necessarily be true. Generally, a local municipality owns the sewer (there are exceptions, and this may be one). If the local municipality owns the sewer, there is no way they will let you dig down to the mainline sewer and tap it; nor should they. Also, that mailnine sewer could be 9 or 10-feet deep; or more. It would be rare to see one that is not at least 6-feet deep. Are you prepared to excavate that deep for how many ever feet?
Now if you wanted to excavate starting from the end of the existing sewer lead, that may be a more viable alternative. But again, the lead could be several feet deep, possibly at least 5-feet, maybe as much as 10-feet.
Permits could be required, maybe several permits. Also licenses for the type of work (plumbing) could be required. Could the approved general contractor do the work - yes; If you have deep enough pockets. Cost - probably in the neighborhood of $500 - $1000 per hour plus materials (once again, depth becomes a major detrmining factor).
Here is what a typical mainline sewer and lead looks like
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