It seems to me that the owner of this E29 has it priced to sell quickly. They can't expect to get top dollar for a boat with an A4 in it. I have no problem with the A4 as my boat of the last 10 years has one in it, but many people consider this a big red flag. The forum at Moyer Marine is the best place for helping you learn about the Atomic 4. The A4 is a simple engine and I have not had to pay a mechanic to work on it yet. The A4 is also quite durable - our A4 and boat are 45 years old.
Did they give a reason for putting it up for sale?
Apparently, Erickson made a standard model 29' and a tall mast version. Here is the std version spec: ERICSON 29 sailboat specifications and details on sailboatdata.com
Do you know which version of E 29' this one is?
Fixing the wiring for the lights
should not require a huge effort.