I'm trying to finish my first quilt - I'm almost to the part where I add back, but I'm unsure of the best way to do this. Should I quilt in sections, or should I just complete the whole thing (should be a twin size) and then do all the quilting? :-D

You will want to sandwich and baste it
Then you quilt from the center out
Square up the quilt and bind it :D:D:D

Hey fellow Marylander. I live in the north eastern most corner of Carroll County. My sister-in-law belongs to a guild that meets in Lithicum. Maybe you should hook up with her.
I prefer to complete the whole top and then layer it with batting and a one piece backing. It is possible to do "quilt as you go" but joining the pieces together is a chore I hate. Are you going to machine or handquilt? As a mostly handquilter I prefer to work with a one piece back, that way there are no seams to quilt through. I would think a one piece back would be easier to machine quilt also. Remember that you will have to fold or roll parts of the quilt small enough to squeeze through the throat plate of your sewing machine.
I belong to two guilds. One in Westminster, Carroll County and the other in Ellicott City, Howard County. The Westminster one has already had their December meeting as they meet the first wednesday of the month. Next week is Village Quilters meeting but it is the Christmas Party so not the best time to visit without a sponsor. Both guilds meet monthly. I think the one my sister-in-law belongs to is Friendship Star. Ask about guilds at your local quilt shop. While we can offer you all kinds of advice and links a real guild can do hands on.
Welcome and keep in touch.

Thanks for the advise. I'm machine quilting.
My sister is doing a quilt-as-you-go but she is having lots of problems with the edges. I thought to do the same, but since I'm lagging behind her, I see all the problems. :( Thinking of having to go through the same problems is very discouraging.