If it's going to be daylight then I don't think you need a recce at all, unless you're really going for a time and don't want to think about navigation at all. Having said that there are a few places you need to be aware of but provided you spend a bit of time with a map beforehand you'll be fine.
Starting from Ivinghoe the first half has more opportunities to take a wrong turn. I've got my map out and will point out where I think you need to take care:
1m in, Ridgeway comes off to the right out of the woods and downhill through a field.
Running through Tring be aware the Ridgeway comes out on the left. Easy.
Right turn just before Hastoe. you pop out of a wood and turn left, then are greeted with a road bending round to the left and a sharp right hander on the corner. You want to go right. This cost me about 2.5 miles 
Fairly easy until Wendover. Once you pop out onto the high street go left and follow straight out of town over the railway bridge. No signs on the high street so it's good to know that you just need to keep going straight. Ridgeway appears again once you cross the bridge.
At the top of the hill after Wendover you want to bear left behind the monument.
Just before Princes Risborough you cross a road and come to a gate. There is a track straight on down a hill parallel to the road, or a left turn, you want the left turn.
Out of Princes Risborough you turn left onto a road for ~800m, then turn right and continue on road for another 500m before picking the trail up again.
Easy for quite a while now, just keep going straight basically. When you cross the A4130 at Nuffield there is a pub over the road and a golf course behind it. I got a bit lost here and went to the left of the pub, I think the correct route is to the right of the pub. Either way, remember that you need to run through the golf course and into Nuffield.
Doddle from here to Goring. Cross the Thames and turn right at the top, signposted I think. Left turn shortly after, again should be signposted but just be aware you will be on road for 2.5k so don't panic that you're lost!
Again, it's simple for a good while now. There are lots of paths crossing the Ridgeway but essentially you keep going straight and it's all well signposted. You will run alongside some gallops and then meet another trail like a T junction, go right here. It is signposted but the sign isn't completely obvious.
When you get to the A34 you take the trail to the right which goes under the road. Simples. Then back to going straight.
There is a road crossing after Wantage monument. In that section there is a fairly sharp left hander with a smaller trail going straight on. Should be ok in daylight but you want to follow round to the left.
Super easy for 10m or so until the trail drops down hill and hits a road (there are lots of these before hand but this is the first one you don't just cross over and carry on). Go left here and follow the road straight for about 1m or so, crossing over the M4. Left at the junction and trail will pick up again on your right.
Straightforward until you get to the A346 at Ogbourne St George. Cross the road and follow the lane down and round the the right then left. You'll come to another T and you want to go right, should be signposted.
After a brief spell on road you turn left up a hill and come to a couple of gates next to each other. You want the on on the left which goes up the hill. Long hill 
The rest should be easy.
As for hills, there is definitely more up and down towards the start, especially into and out of towns. Nothing too scary though. The middle is mostly flat then it picks up again after Wantage. Not as steep as earl
