I bought a used ecm at a junkyard the same year as my car a 2000 chevymalibu ls 3.1v6 do i have to take the ecm to the dealer or could i istall it my self

You can install it yourself. Just make sure that you disconnect the battery before unhooking the old one and replacing it with the used one. Make sure you don't have any static electricity on you by touching a grounded piece of metal around you. Happy Motoring!!!

I believe that is a "flash" prom. So yes you will,I don't think the dealer can flash the prom without the car also tho,computer installed and ready to go. They plug in to the data connector.
The older computers had a prom that you could take out and put in the new one ,the new ones are more like a burnable cd disc.
I would call the dealer and ask before just taking the computer and vin number.

Its already programed if it come out of identical car
same year/make/model/trans/optionsetc etc it should work
are you sure the ecm from junkyard works
you should have brought yours there and tried it on there unit

You have to take it to a dealer or send it out to be reprogrammed because the mileage has to be verified before it can be installed.