Trying To Modify Some Column Data In Some Rows

Trying to change some of the rows in a table specifically one column.
column type is varchar
ex. of data
current desired
$345,434.0 345434.0 (stripping out of $ & commas)
435.0 leave as is
general txt leave as is

having trouble updating data in table
tried using temp table, but update command make it so it won't see table

ex. piece of code
update currency_conversion
set currency_varchar = cast (cast (currency_varchar as money)as varchar)
select * from currency_conversion
where substring (currency_varchar from 1 for 1) = '$' ;

sql 2000
trying to do from query analyzer

thanks
glnsk8ter@yahoo.com


thanks
Glenn