I mailed my 1040A a week ago but had to make make changes. Is it necessary to send an amended 1040A ( marked 'amended') with a 1040X?

If you need to make changes definitely file an amended tax form. You can find the forms on Internal Revenue Service (http://www.irs.gov)

To answer your question, no do not send a regular 1040 form marked "Amended", just form 1040X and any corrected schedules you may have had attached to your original form or any new shcedule you may need to add. It's the form 1040X that's used to make corrections to a prevously filed 1040 series return. Do not redue a regular return and mark it amended, unless you are changing between a 1040nr and 1040, and a few other instances, for example.