Here are answers of some of ur queries:
1.) U can install the new version without any problem. No need to uninstall the previous
2.) For complete uninstall, try following s/w:
http://www.innovative-sol.com/uninstaller/
http://www.zsoft.dk/index/software
3.) avast! & AVG are very good anti-virus s/w.
Download avast!
Download AVG
4.) I think its 7.1.406, better look at their site!
5.) U can set those entries in the ignore list! Just right-click on the entry and u'll get an option to add the selection in Ignore list.