There is not a single good answer for this. Working with vintage fabrics is certainly trickier than working with new fabrics & you didn't say if this was a new quilt created with vintage fabrics, or if it is actually from the 1940's. If it's from the 40's, it's possible the fixative has started to break down & is no longer holding the dye as well. In that case, you could try washing it in Synthropol & then re-setting the dyes with Retayne.
To prevent crocking, you need to reduce the friction. When spot cleaning, you want to dab up & down, rather than rubbing side to side. When washing, you want to use cold water & set on the lowest speed your washer has. Ideally, it would be dried by putting a large sheet out on the lawn & setting the quilt/top on that to dry. Air drying helps because it eliminates the friction caused by tumble drying.
But neither these methods nor Color Catchers are a guarantee the color won't bleed or crock. Crocking, in particular, can happen in the dryer & these products all work in the washing machine. If it was me, I'd check with the person who gave me the top & let her know what's going on to see how she'd like to proceed, knowing that there are possibilities to deal with the crocking, but nothing is guaranteed & laundering possibly could end up changing the coloration of the quilt top.
As to your other questions -- yes, you can buy Shout Color Catchers at Wal-Mart, Target, K-Mart, most grocery stores, etc. And I think either hand tying or machine quilting would look nice. I'd make the decision based on which design best supports the hand applique/piecing -- there are strong arguments either way.