Tascam will sell you a manual. They also offer many free downloads in PDF format. (but not the 424 MkII) Even though their bbs is gone, the rest of the site is still active.
http://www.tascam.com/products/manuals.php
They used to sell a little brush that mounted on the tone arm and swept the record just before the stylus. I used a mini-vacuum to clean the brush before each new record. Worked for me.
The unit will operate properly but it will not look much better than when you sent it in. If they have to have the heads relapped, be prepared to pay more than you can probably buy another machine from Ebay. (Unless it is real pro studio gear)
Being a Tascam fan, I recommended the only Tascam I know of that runs off internal batteries. Sound effect recording is not as critical as music and, usually, it will be modified anyway.
Did you know that the sound effect of the spaceship hatch opening in Orson Welles' martian invasion...
The differences are purely semantic. All of them will give you a perfectly good. operating machine. Refurbish and restore tend to include cosmetic repairs as well.
If you would be more specific about your needs, I might be able to help. I have been collecting and using sound effects for over 25 years. You want a "ship flyby." Is that a spaceship, a steam ship, or an airship? Do you want stereo or mono? How long should the flyby last?