Well one way to do it is take all your existing door cards and seats to an auto trimmers and tell them how you want it done, what materials/colours/patterns.
As for carpet theres different types you can get, 2 peice moulded, 4 peice moulded or 9 peice carpet sets. I have had experience with the 4 peice moulded set and it's not terrific, they're fine if you want a quick and rough job, but they don't fit as well as they claim to. Apparently the 9 peice sets are the way to go, so I'll be trying one of these out next time.
There are carpet sets available on ebay ranging from $150 - $200 depending on what type. Also you could try knox, who are apparently very good (and don't seem to be too pricey).
http://www.knoxautocarpets.com.au/
As for roof lining, there seems to be a whole lot that has flooded the ebay market just lately with a few colours (off white, chesnut and black vinyl), but these aren't the easiest things to put in yourself. I've never put a roof lining in myself but from what I've heard of DIY jobs, half seem to have great sucess and the other half swear never to do it again. So you could get an auto trimmer to do it properly. You can get custom made roof lining for what ever colour you are after aswell.
Hope any of this helps.
