A double layer hammock will need some sewing. If you want an integrated bugnet, zipper-entry, sewing would be required.
RE: 2 people in 1 hammock: I hope you're close, as you'll be stacked up in the hammock, you'll have no choice but to snuggle up, as your weight will drive the two of you into the center. Separate hammocks are a better choice for most nights...
If you just want a hem rolled, check your local dry-cleaners. I'd bet they'd hem the fabrics and sew them to your specifications for less than $20... Lost of people have made hammocks without sewing the edges, but in my opinion a double layer would be better off sewn..
Bugnet: Lots of options, but side-entry limits designs. You may want to consider a hang-over the ridgeline design with weighted corners as you could sew this by hand, and use velcro loops to fix it to the ridgeline.
Tarp: If you're going to make one, you should have some experience with a machine. Silnylon is slippery stuff. It's not that hard, but you'd need a little practice.
Worst case: Try it out! You can always un-whip your hammock and sew it up later! Don't forget your tree straps!
Best of luck,
"Do or do not, there is no try." -- Yoda