Personally, I believe it does matter.
If a few rivets are missing or weld seems are not exact, 99% of folks who view your finished model wont even notice. But, youŽll find that, its scenery and figures, that draw most attention from non modellers, friends and family. Practically everybody can judge whats on display.
The quality of diorama accessories is getting better all the time and very realistic to boot. If you build a dio today, and take shortcuts, your gonna become very dissatisfied with it, in the short-term future.
If you feel yourself, that what you plan using is "weak" or could be better, IŽd recommend putting in some extra effort, and get is as good as you can now! But as Mike says, if youŽre unsure, post some pics and get good some good tips, from fellow modellers, that can easily make adifference. Would also recommend looking through some threads in the diorama section on foilage. It need not be expensive to get good results!