Just make sure you have a printed reservation. I stayed off-site on Harbor Boulevard at the Travelodge, about a mile from Disneyland Resort, and made the reservation to LAX from the hotel, but did have access to a computer to print it out. It was a last-minute trip, sort of, and made Express reservations like 20 hours before my flight. Best I remember, it is best to secure your seat 24-48 hours before.
A tip of $5 should be fine each way, or a little more. Ride is smooth, but busy freeway traffic as always. They take you right to your terminal / airline. Very coordinated. Wouldn't want to be a bus driver in SoCal, though.
This was my first and only trip into Anaheim in 11 years, and I flew into Orange County in early October, so I had to split between the blue shuttle van and Magical Express. If you order online, you can get a 10% discount on round trip or one-way. Still economical.
There is a hub drop-off point at the Disneyland Hotel, so I ended up taking two motor coaches.
I'd do it again, now that I am familiar. Might consider RT in and out of Anaheim than LAX, but still, relaxing at the Bob Hope USO lounge was a cool experience.
Hope this helps.