No need to worry, sweet Clover girl will be totally fine! She will live a much happier, healthier life after she's been spayed.

She should be totally fine with going up and down stairs. Just make sure you keep her quiet for a week or so after her surgery. No running, jumping, rough-housing (either with you or other dogs), and just general roughness with her. Make sure you have them get you all set up with an E-collar (cone of shame) as well. Odds are she'll want to get at her sutures! And it's never a good thing when they pull them out themselves! Yes, they will offer you pain medication and plus or minus antibiotics, but some clients decline them. I'm all for pain control it's not even funny! If the procedure would be considered painful to you, it WILL BE painful to them as well! No baths until after her sutures are removed (if not absorbable sutures, 10-14 days is when they are removed). Make sure to not feed her 12 hours prior to dropping her off, so food the night before but no food/water the morning of her procedure! (But your veterinarian will tell you their hospitals policy!)