If you want a *real* simple circuit for the RS232 level translation, I can outline the 1 chip circuit I did for my SVee6 using a Dallas Semiconductor (now MAXIM-IC) DS275 8 pin "level shifter chip".

I made mine on a small piece of Perf Board (aka Veroboard), small enough to slip inside a "DB9 serial port adaptor" (the sort with a RJ45 connector on one end).

You still need the +5 volts conversion - the simplest way to do this is to obtain the PT1501 for about $10 and use that.

You could build the voltage convertor and level shifter using 1 PT1501, 1 capacitor and 1 DS275 chip - you can probably order those from Digikey or similar and maybe Radio Shack - if you're real lucky. You might get all those for under $20.

Make sure that the PT1501 is mountedn well away from the antenna of the GPS - otherwise the GPs may not lock on to the signal well or at all.
[you could probably put the PT1501 inside the metal case of the GPS to shield its RF from the antenna - but make sure its properly mounted and can't short out.

If you want a photo of what I built - post here, and I'll put one up later today (about 5 hours from now) when I get home.