How much for heater core replacement??

I need to replace a heater core for my Ford Escort LX station wagon 1.9L, 1995 right away as I got prenty of steam came up inside and the engine was about to over heat!! I've been smelling anti-freezing inside the cabin while I was driving for a couple weeks, so I am quite confident that the heater core has a leak to be repalced.
As I read you guys comments about the heater core, it seems that the part itself costs like $45 to $90??, however including labor the total cost will be like $500 to $600?! Is that the reasonable price? I read a manual so that I understand the heat core installation involves intensive hands on work.....but I am little scared to bring my car to a mechanic and will have to pay ~$600.
Please let me know how much you think will it be reasonable?? At least I would like to get some ball park before I go to a shop so that I will know if they are asking me too much or not?!!
I appreciate any comments and suggestion for it, especially if you know a good & trustable shop in San Diego are that I can bring my car to, would be great!!

most shops i've been to have between $50 and $75 hourly labor rate... your heater core is easily an all day job...so however unreasonable the cost may seem, your estimates seem fairly accurate...

Thanks for your replay.
I was afraid that my estimate (up to $600) can be reasonable after I read all the hassle other people have done to replace the heater core! If I want to do it all by myself, do I need any special tools?? I have two different companies manuals and printed out some of the comments / step by step procedures from this forum. If there are anything would help me do the replacement smoothly, please let me know! Any comments, suggestions, anything to watch out for based on somebody who have done this before will be greatly appreciated!

Hey MT, torx tool set, metric tools, take your time do not force and if you wreck the clip that holds the speedo cable to the speedo senser( like I did) bailing wire works cause ford don't carry 'em. Also have some new padded tape to help the heater core take up slack inside the heater box- you'll see.

Get the ford heater core, look carefuly where the heater control cables hook up, and you do not have to undo the A/c at all OOps! Good luck