nice snowy winter so far....Eh !
yeah, for once we have it before march

is any type of pullup/down resistor required on the adc input, or would that cause inaccurate readings ?
Not really, but depending what is sending you the voltage... the main concern is more the output impedance your sensor show to the adc. It MUST be lower than the maximum recommended in the datasheet. Adding a simple 0.1uF capacitor is also handy to smooth the results.

And according to your calculations, would upping the sample time to 20uSec be better and how do control the input impedance to get the right value?
well you're really not as this off. 1uSec is nothing, and you're using the slowest conversion clock, so i wouldn't worry to much about that now.

Also, how do I convert my adc "A0" value to volts?
simple maths. 1024=5V
(ADCResult*5)/1024

put 512 as adcresults, and woohoo, you have 2.5 v. but yeah, PBP don't work with floating points... so you need some maths again.. Depending of the accuracy you want, you may use a variant of the above. say
(ADCResult*500)/1024

512 return 250? 2.50 volt.

You need to care about the overflow, */ could be used.

Bellow is a short example of it
http://www.rentron.com/AD_LOG.htm