ALL my son's "friends" get regularly washed in the machine and dryer on normal warm/cold and low heat. Frequently. As in every couple months. They've survived well for the past 8 years. I stick bandaids over the eyes to protect them from being scratched. Only one (talking Stitch) do I NOT do this with ((Note: Disney, you need to pony up and start making the electronics removable!!! It wouldn't be that hard! I'd pay double!)) The MOST IMPORTANT THING is to dry them on low or no heat... or fur can come out wonky.
For Stitch I take a scrub brush, shampoo, & water. I clean it by scrubbing it with the brush and soap addind water only to the brush... then use a wet towel to scrub it it "rinse" it... then use a dry towel to scrub it to mostly dry it... then leave it out.
I would STRONGLY suggest getting a 2nd USMC Bear now, while they still make the same type. Use him as an experiment to run through the wash brand new (This machine has been tested on animals ;) ALSO if he stands up, you've got yourself a replacement lovey if the "unthinkable" happens.