[need advice on pool heater]

I am presently looking for pool heater for an in-ground 16x32 Kidney shape

seems like I would require a heater in between 80 000 to 100 000 BTU.

I have been looking around for some used heater and I came across a Thermeau TH-100, looks like it would fit perfect. The owner also had a 16x32 pool. he is asking 1500

 

I just need advice on this model. Is it good? reliable?

I know other name brands like hayward, pentair, raypack...but not familiar with thermeau

[coping]

I just realize that about 8 inches of the end my coping is cracked so sometimes the liner pops off the track.(right next to my walk in stairs), so I really can not snap lock 8 inches of the liner. So I hang the liner back in place.
My liner is only 4 years old(fairly new). My question is.....is it possible to change just a section? can I change the section if I lower the water in the pool?(if so how much water do i lower it to? Am I taking a chance on trying to fix the coping and risk damaging the liner by not able to put it back on track?
or
Do i wait until the liner has to be changed to change the section of coping?

Also if anyone know what type of coping I have? I think is kafko snap lock PVC