Ramin,
ME 6.x, it is based on Eclipse 3.3 and ME7.1.1 is based on Eclipse 3.4.1. The best would be to download the all-in-one installer from the site. Ensure that the file size and md5sum matches that of the download.
It is better if you can install it in a separate directory than your old ME 6.x
If you wish to use Eclipse to install ME7.1.1, then download Eclipse 3.4.1 classic and use the update site.
Best.