You can get some really good ideas on the internet from people about your options and how to go about them, but the reality is the potential for you to get hurt or killed is pretty high given your knowledge of electrical.
Me personally.... if you don't know anyone that is an electrician I would hire a local electrician to come buy and spend an hour or two investigating your options and whats going on.
He will know how to open the panel and close it up. It sounds simple, but if the past owner hired a shotty electrician he could have created a hazard behind the panel cover and done something to get by which in reality you wouldn't know whats up or how to react to it.
I've been an electrician for 12 years so thats my
