Spectator campside Les Combes is outside track but right next to it (have a look at google maps). It can be reached by taking the N62 from Malmedy up towards Les Combes (this is the old track, going through Burnenville in opposite race direction!), I believe the entrance is on Route des Combes, right on your left when arriving on top at Les Combes. Don´t know if the campsite is already accessible a week before the race.
Keep in mind this is a racing spectators area with all the (German) noises that come with it - all the way thru the nite if you´re lucky. Not much difference with Le Mans and Nurburgring now that I think of it!
And it´s quite hilly too.
There are also good regular campsites near Stavelot
here and just north of the track,
here. Only familiar with the former which is definitely worth a recommendation imo. If you have time I´d suggest you´ll have a look at them both.
Enjoy, I´m sure you´ll love your time at Spa!
