Hi Ron,
The pressure gauge will tell if you're taxing the pump. What kind of pressures do you normally run? 15 years? Part of me says if it lasted this long then it's good for another 15. Joking. Really depends on what is causing the noise. One or both of two things. Water pressure seal or bearings. The fact it is at times quiet still doesn't point to one or the other.
If you do replace it and that size has been working fine then stick with the same and save electricity. As for the solar 25' in the air, once it is filled with water it may as well be laying flat on the ground. Takes a little more poop to get the water up there but once filled, gravity helps on the downside.
Tell us the pressure and that may change our thoughts.
Al