Oh boy. First of all DEFINITELY make the trip!
Disneyland is SO different than WDW. I visit WDW annually, and even got married there, but I have lived very close to DL for 16 years and it has my heart.
You need, at minimum, 3 days as a first time visitor. I would recommend no less than 5, personally. You cannot, in any way, get through Disneyland park in one day. It has SO many attractions (about 55). Disney California Adventure is easier to do in a day, but you would miss out on a lot of the more unique things, like bars/lounges, the Animation Academy, Blue Sky Cellar, live music, etc.
It is VERY different than WDW. For starters, there is no My Disney Experience and FP+ nonsense. We have this magical thing called Maxpass and it will make all your fastpass dreams come true. Similarly, you can't made ADRs 180 days out, just 60. In fact, they are not even always needed, as you can walk up to almost every restaurant and be seated if you are willing to wait a bit. On that note, food is better at DL, in my opinion, especially counter service. CS food is next level at Disnsyland with so many unique options that would only be available at TS locations at WDW. We have all kinds of cuisine here, and it's almost all amazing.
Everything is kinda connected. Disneyland and DCA are across from each other, separated by less than 100 yards. Downtown Disney is just outside the esplanade (area between parks). You can exit either park and walk to DTD in about a minute. The Grand Californian hotel is located midway down Downtown Disney (it's like a narrow, long shopping and dining district) and that hotel is connected to DCA. It has a private entrance into DCA. The Disneyland hotel and Paradise Pier are located beyond the end of DtD, and across the street from the Grand Californian.
The best airport is SNA (John Wayne Orange County). It is about 20 minutes away from theresort, has onsite car rentals, and is efficient, modern, and kind of small. It's my favorite airport in the area.
VRBO isnt really the best option. Many cities in Orange County have laws banning residential vacation rentals. Anaheim allows it, but there are only 200 permitted properties in the city. It can be a sketchy city also, with some very unsavory areas, so I would not recommend that. There are plenty of hotels surrounding the parks, many within easy walking distance. Pick any hotel on Harbor Blvd between Ball Street and Katella Avenue, if you want to be able to walk. There are all price points there. But, for the full experience, I recommend either the Grand Californian or the Disneyland Hotel.
For the record, I used to like WDW better. Lately, though, WDW has taken a nosedive in terms of how enjoyable the experience is. Disneyland is tops for me at this point. It's just SO much less stressful and there is a charm there that is simply missing altogether at WDW.