shirogr - I'm also working on a match-3 game right now. I've actually chosen to make 2 versions to work on simultaneously; 1 with an array and 1 without an array. Each time I get stuck, I hop over to the other one and catch it up to where I was in the other one and then work on advancing with that one until I get stuck again. It's helped me get unstuck in multiple situations and has really helped me understand how things work in C2 and its idiosyncrasies.
With that said, as far as I know, you can't "merge" arrays indices. Visually, you'll be able to, but not logically within the array.
You may need to try something on the lines of - Once a match is detected, visually merge the cells together to create the new sprite, then delete the old values from the array and insert the new "merged" sprite value, as well as the new falling sprite values in the appropriate array indices.
 My brain starting hurting when I was attempting to make my match 3 with an array, so I downloaded the Board plugin from rexrainbow and it made things a whole lot easier. There's a small learning curve for his plugins, but the time spent learning them is far less than the time you spend being stuck. [/edit]