Well,I'll check the chip but in some pics there is an adcon0 or adcon1.If there's an A/D on chip ,there's an Adcon somethin'. Rest assured what you want to do, can be done.Why not post what you have concerning that section of code.It sounds to me like you might be missing the several things necessary to get things rolling.Don't feel bad,there is a very quick and exponential learning curve to use the I/O as analog intputs.
If you want to tack on just a tiny few more components to the front end of what you already need for your photo cell(there are some very cute sot-23-5 comparators from digi-key that several manufacturers make or you could 'brew' your own with a mosfet transistor and voltage divider using your photo cell),you could use the PIC strictly digitally and use a less expensive pic.Way overboard,speaking,there are complete ,3 pin,brightness control chips by panasonic but stupidly expensive for your needs.