Ann...You can just remove what is there or add more batting then stitch back or add a zipper.
Yes, add batting.
If you are referring to the smelly inside part, then just launder as usual. Put white vinegar in the final rinse, dryer dry for fluffiniess.
Ann: take it to a laundrymat/washateria and use a a big machine!
Then: I always use a blanket inside of my dog's bed... as that is easy to wash at home.
Wash the dog bed. If your washer is not big enough, take to a coin laundry and do there. Mine get washed regularly.
If it needs more stuffing, you can add foam or quilt batting.
add cedar shavings from pet store or horse/tack/feed barn/store to insides smells good & also repels bugs; is the suffing contained inside secondary cover or loose in cover? is there a zippered outer cover? take them to laundromat wash on delicate with cold water and woolite in largest washer available for bed size, then dry light warm setting taking out and fluffing stuffing so it doesn't get bunched up do it often as drying continues.what kind of bed is it? foam with back or sides? maybe a picture for us would help us determine how to clean it, some you just cannot wash. some you can only spot clean with soap & water. I get from Goodwill old t-shirts, pillow cases,or for huge dog beds twin size duvet covers or futon covers work well and use them as replacable covers or just launder as neceassary.