Hi guys, I have a Lego set I believe is collectors, however I do not have the box and only 1 of the three manuals, I am wondering if it would be worth even trying to sell, I know basically nothing about Lego and just looking for some cash, any help would be greatly appreciated.

the set is technic 8070

The box and manuals are always helpful, but not necessarily deal breakers.
This set can be sold used for around $100.
But the condition of the Lego and the stickers must be very good to fetch that price.

The hardest thing would be finding a platform to sell it on. If you don't already have an eBay account or some sort of reputation somewhere, you'll have a hard time selling a used, boxless, possibly incomplete set.

Your best bet would probably be Craig's List. At least there, people can see it before they purchase it.

If you do have a sellers account somewhere, I'd suggest building it to show its 100% complete and taking a lot of pics.

Forget about trying to get a box, but instructions would be nice, you can find new ones for $3-$5 plus shipping on bricklink. And like @donbee said, if you have account on eBay for example, with some feedback comments already then sell it there. You should be able to get $100-$120 for a complete set, if you're missing few parts, bricklink is also your friend.

Incomplete sets aren't optimal. Use bricklink to verify the parts are all present. If some are missing, look to see how many and how much it would cost to replace them. If the cost to replace the parts + any shipping fees + your buy in + your time < Selling price of set, get the parts and then build the set. Once the set is built, take pictures. If you take pictures of an unbuilt set, you won't get as much interest.

Instructions aren't the most important (since most are available online) but can help with the sale of the set.