Shutting down pgsql

Greetings,

    Is it possible, advisable, or terribly bad to shutdown a pgsql
database with the do.maintenance script running? I have a 12gb db with
about 780 tables that has been running maintenance now for approximately
67 hours, and it is beginning to seriously degrade the performance of
the application that drives. I am running on debian linux testing, with
pgsql 7.3.4.

    So I am wondering if it is possible and advisable to either kill the
task, or shut down the database in order to do some work on it.

Thanks,
Mark Warner.