yep, 1000 miles is a bit overdue
(for future reference, add some lube every 200 miles max)
Its a good idea to clean the chain; WD40 does work, but its a little bit nasty for the rubber o-ring seals (although tsubaki recommend the use of a water dispersant to clean the chain). I personally havn't heard of any problems and if my chain isnt too dirty, I'll clean it beforehand with WD40.
If your chain is really messy, get out the liquid parraffin and the brushes and clean everything off. Let it dry (use rags then leave it to air-dry for a bit...have a cup of tea or something) then apply a good lubricant - I use silkolene something-or-another, its not a dry lube and therefore dosn't need re-application as often, and stands up well in wet weather...but it is a tad messy. A good dry lube which isnt messy is the Wurth high-performance dry lube, but I always found this came off easily in the wet weather.
Apply the lube to the inside of the chain on both sides of the rear sprocket, and add a little on the front sprocket aswell. Best to apply from the inside, since the rotational forces will natrully cause the lube to spread to the outside.
Check all the rollers roll while your cleaning, if some dont then just give them a bit more attention. Check for any stiff / kinked links and pay them attention aswell
Happy cleaning
With the miles you do, you'd be wise to apply some extra lube mid-week, and then have a proper chain clean once a week and re-apply fresh lube
Matt