Difficulty is relative. If you are from Florida doing 20 mile rides then it will be tough. If you are doing 80 miles and 8000 ft every weekend then not so much.
The climb to Neels Gap will be longer but the climb to Wolfpen Gap will be steeper. Just sit down, put it in a lower gear and conserve energy on the climb to Neels. You will be there for a while. Wolfpen will require some muscle and will likely be more painful.
Be very careful on the descent from Hogpen as the DOT has used very slippery pavement patches and crack sealers in years past. There was one year where it was treacherous to the point where motorcyclists were talking about it.
It is late to be talking about proper training - base, build and taper phases with proper recovery. That should have been started two months ago. The thing to do now is go out and ride hills. The longer and steeper the better. Practice seated climbing and heart rate management.
Many locals don't do this ride anymore. It has become a cottage industry complete with high prices and tourists. There were a few years when it was very poorly run - running out of food at rest stops, broken timing and so forth. I hope that has changed and I might try the century this year. Distance won't be an issue but 11,000 ft climbing will be a challenge. Hogback isn't as bad as the Winding Stair Gap gravel climb so I'm not super worried.
-Tim-