Probably a sweet bass for free if you put a little work and/or money into it.
I would skip refinishing it. Waste of money. You really want to plow 200-300 bucks into refinishing a $400 bass before you even get to making it play and sound good?
So here's what I would do (more or less in order):
Take the old strings off. Restring it with decent but inexpensive strings (DAddario, etc...) in your chosen gauge of rounds (flats wont tell you how the pickups really sound very well and cost a fortune). These are just "temporary" to figure out where you're at. Before you restring it, hit it with about a bottle and a half of guitar polish.
So now, you can see how it plays/sounds. If it plays great from the get go, you're all set. If not, get the action, intonation, and truss rod roughed in yourself to see if you can get it close.
If the neck does have issues as some have mentioned is common, time to figure out if you just want to part it out, and think about a replacement neck. Could likely get one anywhere in the $100-250 range that would work I bet.
If you keep the neck, I would give the fretboard a good oil and polish the frets. This should bring it back close to new. The back of the neck is probably finished, and you could sand that down and/or tung oil it if you wanted. I would mask off the headstock and body join before doing this.
Now to the electronics... if everything sounds really good, again, you're all set. Pots, switch, and jack are easy to re-solder or replace if needed. Pickups being P/J should have lots of options for replacements. This would also be a great platform for customized electronics, like adding a series/parallel switch or stuff like that.
The pickguard does look like it might have some of the type of damage KBD mentioned from the jack placement. You have a few options if that' the case. One would be to try to find someone who would make a replacement copy of the original design. Maybe with slightly heavier duty plastic. Or have someone make one in a design that will fit the bass but is closer to a traditional P or J style. An additional option that could work with either of these is drilling the bass for a new side mount jack.
I think if you did some or all of this, you should be able to keep the spending in the $300-600 range depending on how much you do, and might end up with a bass you could hopefully sell for $400-500 after playing for a few years. Which wouldn't be too bad. If you go into expecting that you might be sinking $200-300 that you probably won't get back on resale, anything better than that will be a bonus. But that's why I laid out the "order of operations" like I did, because you can figure out whether or not it needs the big ticket repairs/upgrades before you get knee deep in spending.
Good luck!