I'm replacing the original electric stove that was installed in 1948, its hardwired from the house.

When Lowe's delivered the new stove today and discovered this they said they could not install the stove because the way the old stove was connected. They suggested I contact an electrician and have them install it.

I called around and was blown away at several $400-$575 estimates to install this new stove. I only paid $499 for the new stove. They tell me I need a 220 plug installed, surely it can't be that difficult since the wires are already there... right?

I will need to ask you a couple of questions in order to help you install your new stove.

What is the amperage your new stove requires?
What size and type wire currently feeds your old stove, (see if you can find any markings on the wire i.e. 8/3, 8/2, 6/3, or 6,2), the wire size and # of conductors will determine if it can be used to feed your new stove.
What size, and type circuit currently breaker controls your existing stove?
Who is the manufacturer of your circuit breaker panel?

With these questions answered I will be able to help you install your new stove. The prices that you were quoted are typical for the installation of a new direct line for an outlet behind your new stove, and to install the necessary cord on your new stove.
Let me know if you have any problems finding the answers to the questions I have asked.