I found the top of my drywell rotted and the soil that was on top fell in...i was wondering what to replace with after i clean the rest of the old cover off..

Greetings, I live in Pa and have what is referred to as a "Turkey Mound or Sand Hill" system. There are 2 chambers that the solid waste flows in to, then the liquids overflow into yet another holding tank, which I believe is a 500 gallon tank. When that holding tank reaches a certain level, the sewer pump (Liberty Pump Model # LE51A, which is an automatic pump as it comes with a float that is activated once the float rises to a certain level and pump the liquids into the sand mound. The pump alarm sounded about 3 months ago, thinking I was up to the task, I ran to my local plumbing supply store with the old pump and I was told by the counter person that the pump originally installed was undersized because it only had 1&1/2" discharge when 2" is recommended, which is why I bought the Model # LE51A, it also is 1/2 HP which is larger than the original pump . I purchased the larger pump that was recommended & has a built in float with a piggy back plug. I connected the pump plug and float plug into one another and plugged it into the existing electrical connector. It worked fine for the past 11 weeks or so, yesterday I heard the pump alarm singing in the basement, went outside and removed the cover, only to find a 3/4 full tank. I disconnected the piggyback plugs and just plugged in the pump plug into an extension cord that I ran out there with me. Pump did it's job, alarm stopped, it was then I noticed that the breaker for the pump (which is located on my generator panel) had tripped. I assumed it was due to the high water level & moisture. I drained everything, rewired the electrical box in the tank, reset the breaker & thought all was well. Several hours later, I hear the High water alarm singing again. So off to the cover I went, unplugged the float and plugged the pump directly into the extension cord once again to drain the tank. I'm going to assume that my almost 3 month old float switch is bad only because after re-installing everything, I manually lifted the float to raise it higher than normal, thinking that it would kick the pump on since I had it up so high. The pump did not turn itself on, so I unplugged the piggy back plugs again and plugged in the pump directly into the extension cord and it started pumping it's little heart out. Is it safe to say that I have a bad float that needs to be re-placed already? It's not the easiest of jobs for me to remove the pump and raise it out of the underground tank to work on as I'm physically disabled and the money saved would be better spent on food and rent.. but if replacing the float is the answer, then I'll go through the pain & suffering of doing it yet again rather than calling out a technician that charges a substantial fee just for the house call, let alone any parts and labor above and beyond that... I appreciate any thoughts you might have regarding this problem of mine. Many thanks for your help!