I've never quite been in your situation and I don't know the actual details and cost. I have been in a lot of
other situations and read of other's success and failures. The following is pure guesswork and not detailed research...
You should expect that it needs the engine pulled and have a head repaired. Probably take it to a shop for an expert opinion first to verify that it's likely a head and see which one. There are a lot of Boxsters around Houston, there must be a few good indy shops in the area. Not sure of the cost, but I'd guess at least $2.5k and more likely around $4k by the time it's back on the road.
A replacement '01 - '02 3.2L engine swap will probably cost at least $7k and likely about $10K 'out the door' from a good shop.
$10,916.83 Later
If you are attached to the particular car and have cash, a rebuilt engine may make sense, but realistically you can buy another S model for less than you'd pay.
The most sensible and saddest solution: Stop putting money in and walk away. Sell it for a loss, before you get in deeper and lose more.
Milky coolant.
My last suggestion and probably what I'd really do: Buy a collision salvage car and swap the engine myself. Still about $4k - $5k by the time it's in, but you can recover a lot of that by parting out the rest of the salvage car. Lots of time and garage space required. - to me it's 'recreation', not 'work'.
Best wishes, and we're here to help whichever way you take it.