If your up to it, clean it properly,internally, yourself. Don’t hand it over to your average tech to get it running.
The KWA Vector has very low tolerance to dirt and grease, and is built to high tolerances. Consequently, they are fiddly to run and fix.
Potentially, if the gun is perfect with all original parts and original box, it could be worth upwards of £800 if you have a few mags. That’s to a collector.
If you want a hand returning it to working, drop me a DM, I can walk you through it or do it for you if you’d like.