Ok, first thing you must park your damaged (or disabled) vehicle ANYWHERE on the planet. Then, go to the starport and buy a ticket for ANY random (cheap) planet, but not a ticket for the same planet you're on now.
When you arrive on the planet, STORE you're vehicle using the datapad (ctrl-d), and GENERATE it. It will come out completely repaired.
I've been using this since i bought my first vehicle, because it's really cheaper than repairing it a garage.
It has saved me a lot of credits on the long-run!

Hope this helps you ! See you on Bloodfin!