What was the problem with the frame? Was it the cut that you showed in the upper pics?
What's involved in the service, generally? Is it a full - pull the motor type of service?
When I was looking at 348, one of the things that worried me was that the car was getting older and the mechanics told me that the parts would start getting more and more pricey. Also, it wasn't until the 360 that Ferrari put an access through the firewall, making service much more easy...otherwise, much service involves pulling the motor out, which is pricey?
-S
Daaaaaamn! Daaaaaaamn! That is an expensive 30K service.
At least they don't come very often... What would that same service cost on a more complicated/electronic Ferrari like a 355 or 360?
Hopefully, all I will need to do is oil and filter changes for the next 4 years

Stan - it is a full major service to be performed every 5 years and/or 30,000 miles whichever occurs earlier. The engine and sub-frame comes out and cleaned, the heads come out, the timing belt and water pump are changed, cams and belts are degreed, new spark plugs, re-paint the cam covers and any of the engine bay parts that need it, radiator flush, a/c flush, engine oil replacement, brake and clutch bleed and flush, and some other stuff.
The cut frame was done by some idiot who thought it was a good idea to avoid dropping the engine and do the service by removing the fuel tank and then ran out of space. He then stupidly cut the frame to get the job completed.
Surprisingly the 348 frame is so beefy that there was no discernible issue in the handling department. I tracked the car 3 times without sensing anything was wrong. Also the Pre-purchase inspection did not detect this problem. You only find it out when the engine is dropped.
True statement about parts being expensive for the 348/355. Also a true statement about the timing belt replacement through the interior of the 360 - a quicker and cheaper process. The major for the 360 would run about $4k if you do the belts, degreeing of cams and the rest of the activities detailed in the paragraph over. However, the clutch service on a 360 will cost about $4k compared to $2.5K for the 348. So they are nearly the same over a 5 year period.
But any servicing cost savings you get in the 360 is peanuts compared to the depreciation. If I had bought a 360 in Nov 2006, I would be looking at depreciation of about $40-50K versus about $6-8K for the 348 - enough money to keep the 348 serviced for next 25 years!
Keep in mind that the parts costs for the 360 will also go up in the future as the model ages.

And there may be new issues that emerge which don't necessarily make itself known when the model is during production. For example, it took some years to find out about the valve guide, header and cats issues on the 355. And only now, we are learning about the header issues on the 360s.
Another point to note is that with increased electronics in the 458 and California, you are slowly but surely being forced to go to expensive dealers. Ferraris are making the SD3 and future readers to be limited in availability and super expensive in cost ($15K for a SD3 reader). This is going to drastically reduce your servicing options.
One of the respected independent techs of Ferrarichat has stated that he will not service cars newer than the 430/599. Period!