Caring for a Three Legged Dog or Cat

I rescued my Dachshund when she was 22 months old... She is 4 years old now and as of April 6th 2012 she become my 3 Legged Mama Girl...
I thought she hurt her paw/leg cause we noticed she was lipping so we checked her paw and leg and nothing was there , week later she was still lipping and then i noticed on her shoulder a VERY large knot- so i took her into the vet, Well thank goodness we did..
within 20 mins they come telling me they have to Amputate her right front leg... I was devastated they thought they wasnt going to be able to save her cause they thought she had bone caner from how the large mass was on her shoulder bone.. to make things shorter The Biopsy came back for Sierra she has Chondrosarcoma Cancer- they told me its very rare for a dog her age to have this and very rare to have it in the leg .. It's usually in the nose.. The vet told me she will be fine, they are 100% sure they got it all..
In 3 months we will get a full xray to be sure that nothing spread.