I get asked this now and then and I tell everyone the same thing. I won't do the decals unless I restore the entire cabinet, inside and out. Most everything inside the cabinets has to come out in order to do this and it doesn't cost much more to clean it all before putting it back in.
$1250 if you pull the playfield or $1500 if I have to pull it and put it back in. When you get it back, it'll look brand new.
There're guys around that'll do just decals for $500 or so, but why not do it right if you're taking it that far.