Firstly welcome to the forum Doug!
First thing I'd be doing before even going near it with 'special' tools that you've stated you don't have (or the budget for at this stage, and don't need) is stripping it down and giving everything a good 'de-crudding'.
You didn't say if this guitar has a maple or rosewood(or any other dark, unfinished) fretboard. If it's the latter then it's ok to use a 0000 steel wool over the whole board (i.e, you don't need to mask the wood), that's usually only carried out for boards with some sort of paint finish or white wood. Unless it's had excessive playing whilst hanging in the shop, you shouldn't really need to be thinking of any fret leveling at this stage. Just check fret ends for any lifting (look for any gaps between the underside of the fret and the board that appear to be bigger on some than others), sometimes these just need a light tap to re-seat them. If they don't it will mean a bit more serious work but don't worry about that at this stage. The gaps in the fret slots you mention, I seem to remember (it's been awhile since I've worked on an Ibanez) that Ibanez usually left the tangs short and filled the slot with a bit of appropriately coloured filler, this may have just come out but it's unusual if it has. May just require a bit of refilling, tangs don't need to go all away to a board's edge to work correctly, it was just easier for production to leave them that way on an unbound board.
Remove the bridge and strip it down (usually only requires a phillips screw driver and an Allen key), hit the jammed fine tuners with a shot of CRC or WD40 and leave it soak in for a bit before trying to get them to move, maybe that you'll need to just work them backwards and forwards a little at a time until they free up. String locking bolts may require the same by the sounds of it. If everything is particularly bad you may need to soak the whole bridge in a jar or similar, once you've removed it from the body.
If you are unfamiliar with setting up intonation
make sure you take a note of how far away from the front edge of the bridge each saddle is, before removing it so it can go back in the same place when you reassemble (that's providing the intonation is set correctly already!). Soak each part of the bridge in white spirit/shellite (available from Bunnings) and scrub each part with an old tooth brush....or a new one, just don't go brushing your teeth with it afterwards!

Then re-assemble the bridge. Give the rest of the guitar a good cleaning and maybe even hit the pots with a bit of electra clean if they are at all abit scratchy (Electra clean is also good for loosening/cleaning any hard to move crud on any finished areas too, it doesn't harm the finish)
Once you've reassembled everything,this should bring it back to a good starting point to adjust things like neck relief, action e.t.c.
Good luck bringing your purchase back from the dead
