First of all, F%^& Comcast. Evil, corrupt, incompetent monopoly of a company who routinely violates their promises and raises rates on customers without justification. Our internet service with them is lightning fast (~600mBpS) but they just jacked the monthly bill from $117 to $147 and say there is nothing we can do about it. Infuriating. We never really wanted cable TV service or a phone line from them, but it all comes on the same coaxial cable together and they play games with the pricing to make you combine services. It's all the same data to them, and a coaxial cable is pretty future-proof as far as data bandwidth and available services go.
ANYWAY, I had the same exact scenario as you when we built our house some 800 feet off the road. Comcast initially quoted us FIVE THOUSAND DOLLARS to bring service to our house. Our only other option is AT&T phone line, IE DSL at 6mB, which also would have had some infrastructure expenses to bring in. After two months of arguing with managers in our local comcast office, they finally said the same: "if you get us a 2-ft deep trench, we'll lay the cable and install service for your for free". I was not ever considering fussing with conduit for 800 feet - the direct burial cable they supply (Around 0.5" diameter, hard to bend) works great and has no issues. My neighbor has a garden that my trench ran through for 100 feet and he did plow the cable up once! He was terrified because he though it was our electrical service, but no, just the comcast coax. The fixed it the next day for free, all good since. Bob added a foot of soil to this area and vowed not to plow there any more.
So I rented an excavator (bobcat E35) with a one foot trenching bucket and started digging. It was a little sketchy since I had to dig directly adjacent to our primary underground electrical service, but thankfully that trench was 6+ feet deep. I had to go ~700 feet from my neighbors backyard pole, behind his pole barn, through his garden, down a steep 35 foot hill, around some big trees, and to behind my house where they put the pedestal. From the pedestal to the house they just pushed a small coax line into the dirt, I've had to repair that part also after my front loader snagged it (why do I keep digging and landscaping this area? my wife would sure like to know).
In conclusion, F%$k comcast, may they rot in hell, and good luck to you.