You may not be able to Search/Replace within a columnar selection, but you can easily carry out your task within Notepad++. Use Find and Replace feature, with the Regular Expressions box checked.
If you want to remove quotes only from a target column, use the following regular expression in the Find field:
(^([^,]*,){i})"([^,\n\r]*)"(.*$)
Replace i with the position of the target column minus 1.
(i.e.- Us 2 if you want quotes around the third column, 0 for the first column, etc)
In the Replace field use:
\1\3\4
Clicking "Replace All" will strip quotes from the target column.
If you want to blow away all quotes surrounding each element in your csv without prejudice, use the following regular expression in the Find field:
((?<=,)|(?<=^))"(.*?)"((?=$|,))
In the Replace field use:
\1\2\3
Clicking Replace All will strip quotes form the columns.
Example
Since you didn't provide an example csv file, I'll walk through my own working example. Below is my csv:
"0","1","2","3","4","5","6","7","8","9"
"10","11","12","13","14","15","16","17","18","19"
"20","21","22","23","24","25","26","27","28","29"
"30","31","32","33","34","35","36","37","38","39"
"40","41","42","43","44","45","46","47","48","49"
"50","51","52","53","54","55","56","57","58","59"
"60","61","62","63","64","65","66","67","68","69"
"70","71","72","73","74","75","76","77","78","79"
"80","81","82","83","84","85","86","87","88","89"
"90","91","92","93","94","95","96","97","98","99"
"100","101","102","103","104","105","106","107","108","109"
"110","111","112","113","114","115","116","117","118","119"
"120","121","122","123","124","125","126","127","128","129"
"130","131","132","133","134","135","136","137","138","139"
"140","141","142","143","144","145","146","147","148","149"
"150","151","152","153","154","155","156","157","158","159"
"160","161","162","163","164","165","166","167","168","169"
"170","171","172","173","174","175","176","177","178","179"
"180","181","182","183","184","185","186","187","188","189"
"190","191","192","193","194","195","196","197","198","199"
If I wanted to remove quotes from the second column, I would use the below Find and Replace fields
(^([^,]*,){1})"([^,\n\r]*)"(.*$)
\1"\3"\4
Clicking Replace All yields the below result:
"0",1,"2","3","4","5","6","7","8","9"
"10",11,"12","13","14","15","16","17","18","19"
"20",21,"22","23","24","25","26","27","28","29"
"30",31,"32","33","34","35","36","37","38","39"
"40",41,"42","43","44","45","46","47","48","49"
"50",51,"52","53","54","55","56","57","58","59"
"60",61,"62","63","64","65","66","67","68","69"
"70",71,"72","73","74","75","76","77","78","79"
"80",81,"82","83","84","85","86","87","88","89"
"90",91,"92","93","94","95","96","97","98","99"
"100",101,"102","103","104","105","106","107","108","109"
"110",111,"112","113","114","115","116","117","118","119"
"120",121,"122","123","124","125","126","127","128","129"
"130",131,"132","133","134","135","136","137","138","139"
"140",141,"142","143","144","145","146","147","148","149"
"150",151,"152","153","154","155","156","157","158","159"
"160",161,"162","163","164","165","166","167","168","169"
"170",171,"172","173","174","175","176","177","178","179"
"180",181,"182","183","184","185","186","187","188","189"
"190",191,"192","193","194","195","196","197","198","199"