Those are reasonable prices. Just find out who the fret 'guru' is in your area and see if that person charges substantially more. Fretwork and fingerboard prep can really make or break an instrument so be as picky as your wallet will allow.
Also, are you planning to use the same brass alloy frets that Warwick installs or are you going to use something more standard like nickel-silver or stainless steel? The Warwick brass alloy is noticeably softer (probably the reason you're having to refret in the first place) but does impart something to the sound of the instrument. If you're not going to use brass alloy, I would recommend stainless steel since it will last much longer.
Don't worry too much about the size. Your tech should be able to measure the existing frets with calipers and give you a couple of choices.
You can get the Warwick wire through a dealer or online:
http://shop.warwick.de/product_info....6-pieces-.html