whenuwishuponastarr --
The thread that
HydroGuy linked above is an excellent starting point for WDW Vets/DLR first-timers.
I will also mention that, assuming you will be at DLR on September 12th or after, you will experience the Halloween Time season at Disneyland (including Haunted Mansion Holiday and Space Mountain Ghost Galaxy), which lasts through 10/31.
If you're not at DLR on September 26th or beyond, you will miss Mickey's Halloween Party (the DLR equivalent of
MNSSHP at WDW), but there are still many things to enjoy during Halloween Time, such as the Halloween Carnival (which is a lot of fun), seasonal treats, the Dia de los Muertos display, the "Pumpkin Festival" on Main Street, the Ray Bradbury Halloween tree (special during the day, but gorgeous at night!), lots of fun, vintage Halloween window displays on Main Street, etc.
Scroll down the posts on the first page of the
Halloween Time at DLR Superthread to see photos and get an idea of what to expect for Halloween Time as far as foods, attractions, dates of other events that could be taking place at the same time, etc. (You don't need to read the whole thread if you don't have time -- it's not necessary.) Skip over the Mickey's Halloween Party references because, again, if you're not there on 9/26 and beyond, that won't be relevant to you. Then, join us in the Superthread and feel free to ask any questions about Halloween Time-related festivities!
If you're at DLR prior to 9/12, then you will likely miss Haunted Mansion Holiday, the Halloween Carnival and Space Mountain Ghost Galaxy, but you will still see a lot of pumpkins and Halloween-ish décor going up around Disneyland. The decorations started to slowly go up in August!
I hope you have a great trip to DLR, and will love it!