I don't have your RV but, in general, some issues and problems can be expected in the first year. Since this is brand new, you always have the option of working with your local service department on the fixes.
In my option, the leaks are concerning and need to be addressed immediately. There seems to be a manufacturing issue that needs to be corrected. Maybe a simple adjustment of the slide that your dealer can check out for you. Does the a/c leak during and after a rain or is it condensation? Sorry I can't help more.
I am sure you will get some other Lexington owners to chime in, but you might want to check out the Lexington forum
More general to RVs is a recent thread asking pretty much the same question: How many things have gone wrong with your trailer the 1st year you had it?
Sounds frustrating and I wish you the best of luck.