Hi, Tim ... this likely will sound like a little bit of a copout but it's almost impossible to comp a house in Sun City without either seeing it or some additional details. Among the factors that will greatly impact the price are age, condition, any improvements, any renovations, etc.
Neighborhoods with cookie cutter homes are easy; in Sun City, the molds on either side of Grand Avenue are too different to pull it off.
Shoot me an e-mail off list if you so choose and I'll let you know what I can, at least without interfering with your current agent's ability to sell. You can see my credentials on my blog below; I've had listings in Sun City in the past, though I had to leave them behind when I switched brokerages.
Thanks and take care.