Sounds like a good price to me... even if it some day blows (worst case scenario) - you will be able to recover most of the money by parting it out... a used hardtop itself is worth $600.
Meanwhile, if the engine and transmission are good - other stuff can be fixed or lived with untill you have time/money to fix it.
I bought my boxster really cheap 2 years ago before boxster values tanked. $9300, it was an 02 w 76 k miles w clean title that was in an accident and the airbags have deployed. Everyone told me to run from that car, but I bought it, fixed it up (2 airbags+2 seatbelts+ bumper cover ~$1500) and couldn't be happier.
If you can turn wrenches - these cars are not any harder or much more expensive to work on than a honda or vw.
For example some repairs that are possible w 80 k miles: DIY clutch job - $500. M030 sport suspension (Set of shocks and springs on all 4 corners + sway bars) - $1200
brake pads on all 4 corners and rotors resurfaced - $250. key needing a new transmitter if battery doesn't fix the problem - $100.
Of course, if you are not mechanically inclined or expect a 13 year old Porsche for $5500 to be really reliable - you will be dissapointed and should avoid it.
As far as I understand, with 77k miles the porous block would have already surfaced long time ago, but IMS failure may still happen.
Inspection is still a good idea though, even the cheap one as it will let you at least get the car on the lift.
Just my 2 cents. I am an optimist
