Nothing wrong with replacing fluid if it has been a few years just be careful of the paint!
Before you buy pads though if they are not worn out or contaminated with grease, Pull the caliper apart and clean it out. A lot of crud builds up inside the caliper. It is usually white and will turn to powder when you scrape it off with a brass bristle brush.
Following posts on here, I did that with my caliper using a dremel with a brass wheel and was amazed at the junk that came off.
Be sure to really get in the groove that the seal sits in. This is a common issue with sticking brakes.
From there, since fluid is out, give the master a good cleaning and inspect the parts for wear and get a rebuild kit if needed.
On the arm that holds the caliper, clean and grease the pivot rod and set the gap according to the manual.
Very good chance this solves your issue.
