Now I thought about doing my own tutorial for this but I just basically used the same one I've used to make other knit shift dresses, from the lovely Merrick at http://www.merricksart.com/2013/06/mod-shift-dress-tutorial.html. Couple of things I would suggest though, think about the stretch of your fabric when marking the pattern pieces. I used a polyester knit with not much stretch to make a dress a while back, but a very stretchy top to mark out the pattern pieces, resulting in a slightly-tighter-than-intended dress. Especially for Christmas!
I also made sure to measure my neckline properly and baste it to test that it would fit over my head, as I've had problems with that before too! I did quite a high neckline so that the collar would look best, and just sewed it on by hand, after I had finished the dress.
The collar I bought from eBay for just a few £'s, from china, I have to say I did feel a little guilty about that, as when I started making my own clothes I was happy to not be supporting the cheap labour clothes trade. Although as you only need 1 metre of fabric which was just £6, this meant the cost for the whole dress was less than £10. Bargain.
I've made several dresses/tops with Peter pan type collars since I started sewing, and this is first one to get a resounding nod and no criticism from my man, so needless to say I'm pretty happy with it!
I love making comfy knit fabric dresses at the moment, they're just perfect for a smart casual work outfit, and for this country where it's only hot enough to be in light summer clothes for one week a year if we're lucky.