I personally used #555 bulbs in my KI1, but I think the proper one is a #161. #555's are way brighter.

you can get these at
www.happcontrols.com
as for what you're asking with the "P1 coin door thing", are you talking about the coin mechanism, or the coin switch?
it's likely your coin switch may be bad (this is the switch that the coin passes through to register a credit), especially if it's an original part. don't worry about keeping that original, or even the coin mech (coin mechs ensure that your machine only accepts a certain type of coin, say a quarter, or a .984 token, etc.) for that matter, those are replaceable parts that fail eventually.
some people solder the wires on coin switches, some use quick disconnects. in either case though, the wires can become brittle either at the solder joint or the quick disconnects can break off too. I'm leaning towards what you're saying is that the coin switch isn't working, so make sure your wiring is good first.
the coin switch has 3 terminals on it: COM (Common, this is where the black ground wire goes), NO (Normally Open circuit, in this case, a credit will be registered once the wire reaches its home position again after the coin passes through, credits are registered when the circuit is opened) and NC (Normally Closed circuit, where a credit will register as soon the wire goes downward, meaning the circuit opens only when the actuator wire is down, since its home position keeps it closed)
you want your coin switch wire to connect to the NO, which if viewing the switch from the side, would be the middle terminal, with the NC being the top one, the L-shaped one on the bottom being the COM. there's other kinds of coin switches where all 3 terminals stick straight down too, but they're usually ordered the same, with the first being NC, second NO, and third COM. just read the markings on the switch if you're not sure -- probably a good rule of thumb to follow anyway instead of connecting wires randomly.
hope my explanations are clear enough, you can ask around though.