If the covers are still over the idle mixture screws, they're easy to drill out.
I would certainly not pay anyone $650 to adjust the valves. I don't know how experienced you are with things like that, but it's not hard if you take your time and work methodically. The folks here will help if needed. Is there anyone nearby who has been through it and can help you through it the first time?
Here's some information about adjusting the valves:
https://faq.ninja250.org/wiki/How_do..._the_valves%3F