What's wrong with my civic??
 

My car seems to have hit a wall. 1994 civic dx 1.5 liter. In the last month it has:
-heater takes forever to heat up. I replaced the thermostat and it fixed it for about 2 weeks. Now it takes forever again to heat up, sometimes it doesn't.
-engine sputters for 2-3 seconds after starting and then runs fine.
-car makes a loud clicking sound especially when cold. I think it may be the water pump.
-the dash temp gauge has never worked but the car never smells hot.
-oil and coolant levels are fine

What are some cheap things I can replace/check now before taking to a shop? Thanks