Anyone built with WA Housing need some advise!

Hey guys,
So i am a really nervous first home buyer and after giving affordable living the flick I have decided to go with WA Housing Centre. Anyway we have been formally approved and settlement is dated the 28/08/2014. I havnt had pre start and I am just getting worried about cost of things at prestart. Does anyone know if there is a list that gives you an indication of prices for certain things being upgraded/ Changed. My sales rep has basically said that the changes I am wanting will be able to be made at prestart so to wait till then, and now im worried about how much extra its going to cost me. Ive heard reviews that the standard carpet ext is crap so you will need to upgrade, things like that.

The things i am wanting to change or have them include are:
- Cupboards next to range hood
- Extra shower head in ensuite
- kitchen island wider and "wall" addded ( to make picture)

Im also wanting to know if it is very exspensive to get them to do interior painting and blinds?
I went to their display home ( which they said had all their stock standard range in ) and while most things they had in their i was satisfied there were a couple of things i wasnt so now im concerned about how much it is going to cost me !


Also now that i have formal approval can anyone give me an idea on exactly what happens next and how long it might take to have my house built?
Sorry for all of the questions , thanks in advance