The only campsite I know anything about is the one at Dufton, which isnt all that far from your planned walk. Its on the Pennine way and, its OK - and near the pub for post-Cross-fell-conquest celebrations....
I'm assuming that you're wanting just the one campsite - for a circular walk? Otherwise the next official one is at Alston, although you can camp behind the village hall at Garrigill...
Other than that, your plan should be fairly straightforward.. your navigation skills might be tested on Cross fell summit, though - but there's nothing to fall off although there's some slight danger of disappearing down an unmarked mineshaft if you get off the path!