I agree H2ot Sun does have a lot of good information regardless of the brand of panel you end up buying, just be aware a lot of it is slanted toward promoting the panels they sell. While their panels may be superior about freeze resistance, you should be aware that many people are using other (Fafco, Heliocol, Aquatherm, Techno Solis, etc.) / cheaper panels and simply draining them / blowing them out in the winter with no freeze problems. Out of the information at H2ot Sun, pay particular attention to their how to plumb and case study sections, followed by installation guides.
As to sizing of panels it all has to do with surface area of your pool (typically panels sized between 50-100% of the surface area of your pool are needed), not the number of gallons, as well as knowing your climate and your expectation, the easiest thing to do with solar heat is to increase peak summer pool temperatures, as the maximum number of hours of sunlight / maximum northern angle of the sun is on June 21st, so roughly in the middle of summer swim season. Before and after this date there is simply on average less available heat from the sun (baring cloud and other climate issues). By contrast sizing for extending swim season into the fall is a slow loosing battle unless you have massive solar heat panel arrays as you are not only fighting dropping pool temperatures, but less solar heat available each day as the days are not only shorter, but the angle/brightness of the sun is less and less. (The inverse applies to the spring, except you also have the initial heating load to consider) Other factors that apply are angle and direction that the panels are mounted, direction choice is often limited by roof alignment unless you are going to build a mounting rack. Generally speaking for your location a south facing roof works best, however a Southwest of even West facing roof is acceptable, just slightly less efficient.
Once you get the initial ideas down, come back here and we can talk about specifics of your installation
Ike
p.s. I get about 900 sq feet for your pool, which is slightly bigger than my pool which is 800 sq feet. For my Solar installation in Louisiana I used 11 4x12 Techno-Solis brand panels on a SW facing roof ( I was limited by available roof area) which roughly provides me with comfortable 80+ degree swim temperatures from the last frost to first frost of the year each year. Of course my pool is indoors which changes the dynamics some, no direct solar heating, but much better insulation. My installation thread can be seen here
Solar Panel Replacement / Update
