Right, a couple of things:
Firstly, does your project require you to use LED displays, if not, it's far easier to use an LCD text display - plus you can have it show things like:
"Reading = 3.25V" - which is far nicer.
Secondly, exactly what do you want the display to read - a 10 bit PIC will read 0-1023 over it's full range, which by using the default voltage references will correspond to 0-5V. You obviously have to scale this, but it all depends on what you want it to read.
To give you an idea, assuming you wanted it to read 0-5V, you first divide 5 by 1023 - 5/1023=0.0049 (roughly). So to scale the reading, you simply multiple the reading (0-1023) by 0.0049) to get the voltage. So a reading of 468 would be 468*0.0049=2.2932 volts.
Now this isn't really very good, PIC's don't like floating point numbers, it takes lots of space and is very slow - but there's a much better, simpler, way!.
Using simple 16 bit integer maths routines, multiple the reading by 49 (instead of 0.0049), this uses all integers and is small and fast, so the previous example becomes - 468*49=22932. This is obviously 10,000 times too big, but all you need to do is print a decimal point after the first '2' to make it read 2.2932 volts. The important thing is to keep all possible values integer, and within the permitted range - which for 16 bit maths is 0-65,535. If you need to go larger than that, you could use 24 or 32 bit maths - but you could probably scale it within range anyway.
As for a suitable processor, you need one with an internal analogue to digital converter - the 16F876 is one of my favourites, and gives you plenty of scope for other things.