Going to jump in here and disagree with a couple of the above posts.
Firstly, as MrTechnoBarn pointed out, the electromechanical EK is a MUCH RARER version and is highly sought after. On the couple games where they produced both in fairly equal quantities (Freedom, Night Rider), the EM is generally worth the same to a bit less than the SS. However on the games where they ran only a small handful of EMs along with the SS (EK, Mata Hari), the EM version is worth quite a lot more. Because of the small number made, and even less surviving, there are a lot of EM collectors who want an example in their collection.
Also, being an early SS Bally, chances are VERY good that you have battery corrosion damage that is causing the game to not boot. Unless you have high confidence in your repair abilities, plan on needing a new MPU board. There are folks that sell repaired ones on eBay, or you could drop $200 for an Ultimate MPU from Alltek (an excellent board, I must say). Very rarely do the other board need to be replaced, as a such. I doubt that you have ROMs causing it to not boot. More likely would be the ROM sockets (Bally used some TERRIBLE sockets back then, that did not stand the test of time!)
For the nail, you'd have to post a picture in order for us to gauge how much damage is done there. Most manufacturers had a couple nails down near the bottom of the PF as part of the building process that were always left behind.
In terms of price, it does very by region. Around where I am, and with EK being a more desirable, cross-collectable title, what you described probably be around $400. Its really hard to say without seeing the board themselves, because that's where you're going to end up spending $$. A good condition, fully working EK used to sell for upwards of $1k, but right now, $800 and under is more likely.