Yay for Spaz' homecoming! What a great way to start the week.

To answer your questions:

How long did it take other tripawds to be comfortable walking and playing on three legs, handling stairs ...and attempting car trips with only one person.  

That depends on the dog: their fitness level, age and how well their recovery was managed. Try not to compare and take your time, there's no rush. You'll need to walk a fine line between being protective and managing her activity so she doesn't overdo it, while allowing her to be a dog and enjoy life the way she knows how. Generally speaking:

• start with short amounts of activity, 5-10 minutes a session.
• Tripawds should go on shorter, more frequent walks each day. Start out 5 minutes at a time and build up over the course of several weeks to about a max of 15 minutes each walk (that's the most any Tripawd in typical shape should be walking when they're at their most fit).
• Emphasize brain games over physical activity.
• Car rides depend on lots of things. If you feel more comfortable with her seat belted in while you're driving, try using a doggie car restraint little by little to see how she adapts.

I hope this helps! Enjoy your reunion!