James:

You are in for a lot of fun!

Darkrooms can vary greatly - I have worked in everything from my current converted for temporary use bathroom through a small 4' x 6' room with no plumbing under a set of stairs to a moderate sized special purpose three room set complete with water temperature controls and all the way to darkrooms supporting an extensive photography department in a large daily newspaper (15+ photographers) shooting black and white film exclusively.

To get a sense of the variety, I would suggest browsing through the Darkroom Portrait threads and the Bathroom/Temporary Darkroom thread at the top of the Darkroom Equipment subfolder here: http://www.apug.org/forums/forum43/

Don't get too concerned about the diversity of examples - it just shows the opportunity.