Hi Mike,
My (now) wife and I trekked these areas in 2000/2001. We did it independently, catching a bus to Jiri and hiking for 5 or 6 days before getting to the usual starting point for an EBC trek at Lukla. Its definitely worthwhile starting at Jiri if you have the time, as this part of the trek is much less crowded and gives you excellent training for the higher altitude walking that you'll do after Namche. I dont remember the times and numbers exactly, but the route from Jiri heads east while the ranges run north/south. As a result there is a lot of up and down - I'm sure most days would have included total ascents over 1000m, which isn't possible after Lukla.
We just stayed in "teahouses" along the way and used a Lonely Planet trekking in Nepal guidebook.
Highlights after Namche included the monastary and views at Tengpoche;catching sunrise on Everest on New Years Day from Kallar Pattar; taking the (easy) mountaineering route from the Khumbu valley to the Gokyo valley via Cho La pass; views from Gokyo Ri and Renjo La; and I'm not sure if this was a highlight or not but the flight out of Lukla is an experience not to be missed
I think we took about 22 or 23 days for all of that. We went in Dec/Jan (winter) which meant it was extremely cold of a night (-30 at Lobuche) but much less crowded. I dont remember being cold during the days though and we had no rain. If you only had time for one of those valleys I'm not sure which one I'd go for. EBC is an obvious goal but there's not much to see there and the views from Gokyo Ri in the other valley are probably better than the views from Kallar Pattar.
One other thing to mention - dont believe the locals when they say that garlic soup is a good way to prevent mountain sickness. 2 to 3 serves a day for me and I still copped it !