Alright, if we're assuming life formed in around the same timeline as on Earth, that means it would start with archaebacteria, or bacteria that don't have nuclei. Some of the bacteria that fall under this classification are INSANELY resistant to hardcore environments.
From there evolution would take place. Let's assume some of these bacteria can absorb methane in a process similar to mitosis. Mitosis is the process of water going in and out of a cell to maintain cell structure and it helps in various other functions. So from here we're forced to look at the question of "How does it get energy?" A process similar to photosynthesis might work, using the intense sunlight as a source of raw energy and the extremely reactive chemicals and elements that would have to exist, especially methane, to produce a usable, working form like ADP and ATP. (Adenosine Diphosphate and Adenosine Triphosphate)
It would most likely involve chlorine and fluorine. This is because chlorine and fluorine have pretty high energy outputs when mixed with Methane and react VIOLENTLY with light. So it would probably absorb the chemicals necessary and act as an autotrophe. (Produces energy on it's own)
From there, basic evolution would occur. Eubacteria (Bacteria with nuclei) would form. Later, they would form multi-cellular organisms similar to fungi and plant life. Then once heterotrophes (Eats others for energy) started forming, they would probably absorb things lower than it in the food chain and use some kind of limiter to prevent too much energy from being expressed at once. Other elements would be used to form solid structures, such as shells or organ linings. Metals would be most likely bone structure, with lighter elements forming softer solids. It'd be the same as how calcium forms our bones.
Genetics would probably occur using freons. Freons contain carbon and fluorine. Maybe methanol, formaldehyde, nitromethane, chloroform, or carbon tetrachloride would replace Adenine, Guanine, Cytosine, and Thymine. Transcription and translation (The process of writing RNA and the process of forming amino acids), occurring in similar way to ours. Mutations would occur in a similar fashion as well. Something interesting to note though, is that temperatures wouldn't matter to them, with all of the chemicals and elements found there having a high enough melting point where that is no longer a problem.
If we approximate using the lifespan of life on Earth, it's now been about 3.8 billion years, with archaebacteria taking up about 1/3 of that time, eubacteria another 1/3, and plants about 1/6, with animals and heterotrophes taking up the rest.
Hope you enjoyed this answer and found it interesting!! ^-^
All of the information involving methane can be found here in detail:
http://scifun.chem.wisc.edu/chemweek/methane/methane.html
