What caliber? What vintage? Was the estate the original purchaser (meaning: is the history known)? Is it a special model?
Some thoughts ...
New-in-box Marlin 336's can be had for about that price now and then, generally a tad higher. Special vintages, models, calibers can bump the price. I don't have my gun prices book handy, otherwise I'd check. A quick glance at GunBroker recent sales show this.
Sounds like a fair price, with some potential to be a good value if it's a special vintage/caliber.
Check for standard use indicators of condition: bolt condition; barrel/chamber condition; mechanical operation; evidence of after-market tweaking (particularly if a special vintage). About the only other nitzy thing to check would be headspace, but if the history's known and it hasn't been fired much it's unlikely to be off.