Options:
1. Keep it all, degrease, lube etc but has in increased risk of jumping and chain sucking on your ride.
2. Change chain and expect to jump on the back and suck front
3. Change chain and cassette and poss suck front
4. Change the whole lot.
If you do want to do something I would prob choose no 2 and then try it on a short ride and see if you get away with it – prob not – and prob end up going choice 3 or 4.
Once a week for a year in dirty condition prob would at least stretch the chain and if its more than .75 % stretched then it will abnormally wear the rest of the drive chain:
http://www.cyclistno1.co.uk/features/maintenance/chain-maintenance.htm