Welcome!
Oh, don't worry -- no one is expected to comb through all the pages, so you did the right thing by just jumping in and joining us! There is some basic information on page 1 of the thread -- and some of it may change from year to year -- that could be useful. But otherwise, feel free to ask a question at any time, or just join us to chat about what's happening for the Halloween Time season this year (none of which is really known at this point, but I and other people will post updates, news, rumors, etc., if we find out anything). In fact, I will soon be switching us over to a new thread just because of the page limit issue on this one.
As Corinna mentioned, there will be a party on Halloween night. There is always a party on October 31st, so you will be able to catch that one for sure. Otherwise, most likely there won't be any other Halloween parties during your trip -- though that could always change. Last year Disney threw in a random Sunday night party that I was not expecting, so you never know -- they could very well add in a party on 10/30 too. But, if not, you will have 10/31.
You could head out the week before and possibly have a couple of extra party nights from which to choose, but at this rate we don't know what those dates would be.
The specific party dates should be released in early-to-mid July, via the Disney Parks Blog. That's also when the Cast Members on the phone at Disneyland will get the information, but they don't get it any sooner than when the Parks Blog gets it. All tickets should go on sale to Annual Pass holders, Disney Visa Card holders and Disney Vacation Club members within a week or two of the announcement of the dates, and many of those tickets will be slightly discounted. The tickets for the general public should go on sale one week after that.
As for general Halloween Time dates and info, unless there is any kind of significant change to the offerings this year -- and I guess that would apply to the Halloween Party as well -- that, too, should be released in July. if there is anything out of the ordinary happening for the season, the Parks Blog may do a blog about it earlier than July, but July is probably the safest bet for official info.
California Adventure -- from 2010 and beyond -- has pretty much been stripped of any Halloween fun, for the most part. There are some loaves of bread shaped into pumpkins and other edible goodies, and merchandise, of course, but as far as Halloween decorations and entertainment in California Adventure... the pickins are slim!
Disneyland is where you will find the bulk of the Halloween Time fun -- again, unless something changes this year. There are Halloween decorations and things to see on Main Street and in Frontierland. Space Mountain Ghost Galaxy is in Tomorrowland. Haunted Mansion Holiday will be going on at that time. Characters will be out in Halloween attire. There used to be a Halloween Carnival with pumpkin carvers, games, and lots of rustic decor -- but that is gone forever.
At the Disney hotels, so far there isn't much to see or do that is Halloween-themed, although the hotels do give out candy to trick-or-treaters on Halloween, and the Grand Californian Hotel may or may not have another one of these in the lobby --
https://disneyparks.disney.go.com/b...in-disneys-grand-californian-hotel-spa-lobby/.
Edited to add: One thing I forgot to mention is that you will probably see the beginning of the crossover time, when the parks transition from Halloween Time into the holiday season. The holidays won't officially begin for at least another 10 days after Halloween, I would guess, but the holiday decor slowly begins to go up even before 10/31 in some spots, and then it picks up steam after 10/31, with more holiday decorations appearing every day.