There is a very thorough thread on apron removal, but this is the short story:
For a 1953 square dial, all you have to do is loosen the ten SHCS and the apron will simply come off. However...
Before you start, if you don't have a second strong person to help you, get over to Harbor Freight and get one of their hydraulic lift carts. Mine has been an absolute life saver.
First, drain the oil from the apron sump (pipe plug at the left end) and from the feed shaft reservoir (pipe plug underneath). This will reduce the mess later.
Second, place some 2x4 or 2x6 lumber front-to-back under the apron. It is a heavy beast and you don't to be wrestling with it as the last screw comes out.
Third, replace one SHCS at each end of the apron with a length (4" or longer) of threaded rod with a nut on top. This will allow you to remove the other eight screws and then gently lower the apron onto the lumber. From there you can lift it onto your work surface.
There is an oil channel between the apron and saddle which is sealed with either a cork or rubber ring. Don't lose it. There is also one oil metering unit in the apron, hidden under the tangle of cotton string that should be there. The other five oil metering units are on the underside of the saddle.
Holler if you have any more questions.
Alan