Caring for a Three Legged Dog or Cat

i just found out last thursday my 9 yr old sheltie has a lyposarcoma. i have had the tumor removed twice by one vet and last yr took her for a second opinion becuz it kept coming back. the second vet never even did a biopsy on it, just told me , after talkin to the first vet, that it was a fatty tumor and they couldnt get it all out becuz there was a blood vessel wrapped around it. they told me to leave it alone til it started affectin her movement. 3 weeks ago she started fallin goin up and down the steps and not wantin to bare weight on that leg. ( its her front left one) than took her to a third vet that told me just by lookin at her that it was not a fatty tumor. he did a biopsy and now she has to have the leg amputated. hes doin the surgery asap (friday) becuz it has not metasitsized yet and does not want to give it a chance to. so if anyone has a pet that your vet tells you has a fatty tumor, please make sure its just that. my new vet this could have all been avoided, but hes very optomist that he will get the whole tumor with this sugery and she will have a full recovery becuz there is not a single thing else wrong with my little girl.