You should not have to worry about shipping games, especially if it is within the US mainland. I'm in Canada and have arranged freight for 2 (soon to be a third) pinball from the US.
What you will need to do is find a freight company, I may suggest you at least get a quote from: YRC Freight (http://yrc.com/)
You can get a quote online, specific the pick up zip code and destination zip code. If you are picking up the the sellers house, chances are they won't have a dock or a forklift so you *will need* to specify pickup with a LIFT GATE. If it is coming directly to your house, same thing, lift gate.
I would (contrary to some others I have read) strongly recommending shipping without legs. Ask the seller to pack it up on a standard 40"x48" pallet. Ideally boxed with a shipping blanket over it or in the original box if available. Final dimensions would probably be around 40x48x60 @ 325lbs. There is a reason Stern ships new pinballs on skids and boxed - it is ultimately safer. Shrink wrap it and carefully tie it down to the pallet. It may take an hour or so to pack it and involve an extra $50 worth of parts such as tie downs and crate etc. Hopefully the seller is not against this.
I like YRC because they have default coverage of $25.00 USD per pound up to 400lbs or something so in almost all cases, their default coverage will take care of any serious incident.
Make it easy for the seller, download the Bill of Lading (BOL) from the YRC Site (or whatever company you decide on) and fill it out, send a copy of it to the seller. He has to give this to the freight company when they pick it up. Ask seller to take a picture of signed BOL from the driver and email it to you. The final copy will have a PRO# on it which is used for tracking purposes. Ask the seller to take pictures of the skid once loaded INSIDE the van so you have proof how it looked at pick up.
Side note: if you ship internationally, you also need a commercial invoice stating amount of game as you would pay taxes on this. The Commercial Invoice would go to your broker. This of course does not apply to you.
It really is fairly straight forward and for me to get a pin from MN to Calgary,AB takes about 4-5 days transit time and runs about $375 - $ 400