Welcome to the forum.
"Give" like in 'free'?
Your talking about $4-6K of value there (new, they were $10K), unless there are some major problems (the overheating may just be a plugged radiator, that needs careful cleaning). Even 'major' problems should be fixable and stay under the value of a running 455, IMO.
Sounds like a good deal for you. Probably can mow 6 acres in that two hours before it heats up. /forums/images/graemlins/grin.gif
Do normal maintenance, such as oil/filter change, air filter, grease fittings, check spindle bearings, take a look at the tran oil and maybe consider changing it as well as the filter.
How many hours on it, and since last maintenance. I've seen 455's running strong with 1000-1200 hours on them.
One would have to be curious as to why they are giving it away (and even a little suspicious too). /forums/images/graemlins/tongue.gif
Another thing to do is check with the Deere dealer and ask for the history on the tractor, from their computer system.