Okay, you weren’t on the mission I thought you were on, but, a completely different one! That’s my misunderstanding of your situation.
That aside, I’ll be perfectly frank with you. The mission you’re looking to get needs 20000 credits in your account. I, therefore, cannot recommend selling off your equipment just yet. How much of that you’ll actually need to clear the mission is up to you, as per the story mission on Nav 4. However, that’s the bare minimum balance.