Hi Junkheap,welcome to the forum, and the world of model railways....or, in your case apparently, model railroads.
Since you seem to have acquired some US -prototype equipment, how much do you know about the real thing?
gaining knowledge of the real thing is quite important, as it allows you to have an idea about what is realistic,and what is not?
I don't know where you reside, but if in the UK, perhaps swapping to UK prototype models may help you gain a better understanding of what you seek?
If you do have transatlantic leanings, then perhaps the forum below will give decent information?
I myself have US models.....I see you have an old Bachmann loco?
Whilst there isn't anything really WRONG with this, you may find it's running abilities to be a bit coarse, wen compared with the more state-of-the-art offerings from the likes of Atlas, Kato, etc.....[and likley, pricier too]
Seeing what other US modellers use is a good hint as to where to go.
again, if determined to follow US prototypes, why not join the NMRA British Region? http://www.nmrabr.org.uk/
For advice, I submit that you try not to do anything too big as a beginner?
Your stated aims may well fall by the wayside if you try to tackle too much too soon.
Given what you are after, I suggest starting off with a small, shelf-size layout of the switching or shunting variety.
This sort of beginning will give you plenty of opportunity to expand your scenic ideas, without getting out of depth.
The sort of locos and stock required need not be burdensome on numbers of cost...what you have already is a good start.
also, given that sheer volume or numbers would not be an issue, your aims regarding weathering, etc, can be achieved realistically...without becoming overwhelmed?
plus, with a switching [shunting] layout, the other side of model railroading comes to the fore, and that is OPERATION?
with a switching layout, so much more can be rung out of the layout, than a simple oval-type.
this site ma give you a better idea of what can be achieved in a small space
At least you now have the web to help you find out more...
when I started US modelling, all I had to go by were a few issues of Scalemodel Trains, a Walthers catalogue, and a book of stamps...oh how things have progressed?