@Katrina Cebrian I’m not sure why you’d even consider this person unless you like patching holes punched in sheet rock, repairing doors ripped off their hinges and cleaning up blood stains in your carpet.

The dark walnut doesn't look bad to I think we'll just replace the baseboard with the same dark walnut stained wood but go with a 3" or more baseboard as opposed to the original 1.5".

Just paintin' er white.My vote is repaint it.Coming from the staining/sealing world, stripping it will not get it all and be a terrible mess and cost a fortune.

To stain you need to sand / strip the old finish, it is more work then repainting. 

The kitchen has grease stains on the ceiling, blinds, and the countertop looks ruined.

Her responsibility has nothing to do with you keeping the infrastructure in shape.Let me put it this way: If there was a leak that caused $XXXXX of damage to the roof and your tenant "saw a possible stain on  her ceiling" would you say that she was responsible for the roof leak?

I would not recommend carpet as it is susceptible to stains/dirt and heavy wear.

Current market rent is $1,750, so I'm leaving about 5K profit on the table each year...They are for the most part taking care of the place, a few stains on the carpet but looks like carpet cleaning will get it out.

I used Fusion grout on the kitchen backsplash for stain resistance and still, there is blue imbedded in areas of grout behind the sink.  

I kind of wondered if something like that may have happened - where they wore away the coating by scrubbing a stain.