My incision is roughly 10 or 11 inches. The lymph nodes in question are in the retro-peritoneum, meaning they are towards your back/spine area. The large incision makes it easier to get to them as they must pull out your intestines and things which are in the way. The lymph nodes in question are also in quite close proximity to the aorta and vena cava (some may even be on the artery or vein, I believe) and as those are the largest artery and vein, respectively, in your body they want as much room to work as possible.
I can post pictures of my incision scar shortly after surgery if you like. I've also got pictures of it 3 months and 6 months post surgery. You can just google RPLND though and find some examples.
I was in the hospital for 6 days. They had me walking a few hours after the surgery believe it or not. Couldn't eat anything for the first couple days while the bowels were adjusting back into place. The pain wasn't all that bad except for walking the first day or two. I had a lot of back pain though which was honestly worse than the incision as the bed was really uncomfortable and I have back problems.
It took me about 6 weeks to fully recover. IIRC my surgeon said at 2 weeks I'd be walking fine, at 4 weeks I could jog, and at 6 weeks I could run. That seemed to be pretty true. Couldn't lift anything more than 5lbs until 4-6 weeks as well.
Also they will likely go ahead and remove all of the lymph nodes in question regardless of whether they are enlarged. I had 22 nodes removed and only 1 was positive for cancer.
I/O - Jan 3rd 2011 (Diagnosis) 95% embryonal, 5% mixed (trace teratoma)
CT Scan - April 2011 (Relapse) 1.8cm enlarged node
RPLND - May 10th 2011, 1 node positive for embryonal carcinoma
2x BEP - Began June 20th 2011, ended July 25th 2011
CT Scan - November 17th 2011 (Clear), February (Clear), May (Clear)