What to do first?

[RedTele58]

I can't remember for sure without going out in the garage and looking, but isn't 80k miles a major service point?
Fresh fluids, check the tires for age, have a good independent mechanic do the 80k and have him give the car a good going over, and you should be good to go.

[paulofto]

If you have an unknown history assume none of the regular maintenance was done. The last major schedule prior to 80K miles was the 60K maintenance so I would do that one.

Check this out:

Maintenance Schedule - Porsche Boxster (986) FAQ