I have built all 3 models several times and want to emphasize one point: while there are a lot of after market kits for these, I built them all with common household items. When I first built them, I was a student and did not have the money to buy anything else (then again, in the last century, there were not a lot of after market kits available anyway), so I used items such as wire from appliance motors people throw out, for gold foil I used the thin gold foil from chocolate wrappers (this way, you have a legitimate excuse to eat the chocolate), plastic from disposable bottles (such as asprin) is always useful, and so on.
The most important thing is to do your research at NASA history sites, and other available sites that show photos of these vehicles from multiple angles. Also, remember that depending on the mission, each craft was a little different so pick one and work towards that. Finally, as you look at the detail, figure out for yourself what level of detail you are comfortable trying to achieve. If you are too ambitious, you may turn yourself off to space craft which would be a shame because they really are a hoot when you finish them. I'm not saying to go easy; you always need to challange yourself to move ahead.
One final item, if you have a space or aerospace museum in your area, go to it and study the craft. Take pictures and always go back for reference.
Bottomline, enjoy these! They are good kits, you will learn alot and always remember that if something does not turn out the way you wanted, you can always redo it!