If a store is charging you $300 just to install a head unit, they're telling you they don't want your business. The reputable shop I went to for a 2DIN install wanted $50 since it's only an hour's work anyway.
Some of the Escape specific websites/forums have pictures and descriptions of 2DIN headunit installs if you are still curious.
Be careful though, it's a slippery slope you're on. If you haven't upgraded the speakers yet, you'll really want to once you put that new headunit in. Then "while you're at it" you might want to sound deaden the doors to improve the sound and reduce road noise...good luck!

 

You're right, now you got me curious about "sound deaden the doors", tell me more!

 

One of the Escape forums (forgot which one) has a pretty detailed description of this. Basically you can go nuts and make your Escape as quiet as a Lexus or just beef up the sound coming out of your speakers. If you have a good installer, they will know all about this as well. The products are sold under names like Dynamat and RAAMat.

 

Crutchfield.com has information on this subject.