hi' - congrats on the car ! sounds like you got a good one!
make sure your coolant cap ends with serial .01 (if not its a 20$ upgrade), you could also check the actual tank for hairline cracks - this is very common on 6 year old boxsters... I happened to my car and ended up costing me a new water pump also + a scary experience with a a lot of coolant dropping from my car !
if you do not have any oil drip whatsoever I would only look to filters and make sure to change all oils and important fluids
Things you can 'expect' to cause problems within a few years could be the MAF (try cleaning first) and the AOS they tend to cause problems... search the forum about this, this is very well documented in case you don't already know everything about this
Enjoy the car as much as possible
Personally I am looking hard for a black hardtop for my car so I can bring it into the winter season.
Regarding leather I can really recommend ColorPlus.com
They sell a excellent cleaner which got the darkness out of my seats. I then applied their soffner and wasnt expecting much as my seats allready felt 'soft' but I was very surprised to experience they got a lot nicer. My next step is their leather color which is mixed from original Porsche color codes to match - I have savannah and I really hope this can perform a small miracle and bring the savannah color back to life... it's a bit expensive though but well worth it!
Another interiour upgrade I really like is a new style steering wheel. If you have the old style 4 spoke wheel, upgrading it to the 3 spoke really made a difference for me.
I don't like the alu packages much (too plastic) of course that is an option, I have seen people who do the paint job themselves with better results imho. One alu upgrade that many prefer is the alu dial bezels or white dials - both cheap.
Painted center console to match the color of your car perhaps ?
www.design911.co.uk has a pretty big selection of Boxster interior and exterior upgrades - my next will probably be new exterior air vents.
And please post pics of the car