I'm sort of the opinion of most here. Seems a little high ... depending ... I'm in western Pa , most pre owned GPs are going for around $500.00, give or take. A little higher at dealers. I just bought a new GP-100 in .22 several months ago ... $610 plus tax and fees. On the subject of the trigger job ... go with caution. If the job was done professionally by someone you trust ... might be OK , but many average jjoes try to perform trigger jobs and make the gun unsafe. I've found simply changing springs and "cleaning things up " works well for me. Also , if it hasn't been fired much , several sessions of dry firing will do wonders.
regards , brushunter