Barb, I think this is one of the best tours for a solo first-time Europe traveler and perfect for a life quest! I found the bonding very different on this tour than on any of the others I've been on. That's a total of 11 Rick Steves tours and 11 Road Scholar tours, lol. I think it's because you are with the group for the 3 weeks and experience so much.
I do recommend you start out trying to spend time with everyone on the tour - either eating breakfast or sitting with different folks at the group meals. You'll learn everyone's name and over the 3 weeks make some lifetime memories. I am not kidding about this.
When you are on a bus transit day, pick up something at one of the Autogrill's you'll stop at for lunch or breaks and share it when you get back on the bus. Some kind of weird potato chip flavor, candy, cookies, just something small and inexpensive that gives you an excuse to stop to talk to everyone. This works really well if one tends to be a bit shy.
Be in the best physical shape you can be in - you'll thank yourself for that.
Make sure you can handle your own luggage - both your suitcase and any bus bag/day pack you might have. I travel solo and while I'm sure someone would help me if I needed it, I want to be completely independent and able to manage my stuff on my own. Make sure your bag is light enough for you to carry up a flight or 2 (or maybe more) of stairs.
IF you hear someone talking about something interesting ask if you can go along (unless it's a totally romantic event). In Venice I heard one group member saying she wanted to go hear a Vivaldi concert. I said me too, as did another person. We purchased tickets from the hotel, I figured out our route, one of the others figured out a restaurant and we headed out to dinner and the concert together. What a fun time.
Also, be ready to take the guide up on any extras they offer. Ours offered an extra group meal in Rome and maybe somewhere else, plus some activities on the "free" day in Switzerland. In general he paid for them then told us what our share was (always reasonable).