Incidentally, NMEA 0183 "speed restriction" is a fairly strange beast. They did for whatever reason define the speed to be fixed at 4800 baud and that certainly does set a very low limit.
However, protocol per-se (i.e. the set of sentences) does not have any specific speed limit and, as it stands, can be used to transfer 100s of thousands of sentences per second (as I currently do in PolarCOM "brute force" testing, primarily over the network). In fact, AIS which is "NMEA compatible" (i.e. uses the same format for it's sentences) tends to run at higher baud rate.
Of course the point of NMEA0183 speed is becoming somewhat moot since (unfortunately, in my view) many manufacturers are switching to either proprietary protocols or to the NMEA2000 (which is proprietary too unless you have a few thousand $$ to spend on the spec, and requires fairly complicated hardware interface, that you can't buy for $20 the way serial RS232 adapters are sold).
Nevertheless, most instrument and GPS vendors will provide either a compatibility output or a separate device that will speak NMEA 0183.
If you do plan on using a computer, use one with real serial port (rare nowadays, nonexistant in notebooks) or spend money on a better serial-2-usb adapter. Most cheap adapters are based on PL2505 chipset from Prolific. While the chipset itself is just fine, for whatever reason (cost savings, production issues?) these adapters tend to be flaky - some will work fine, some will only work on input or only on output and others not at all. More expensive FTDI-based serial-usb adapters tend to be more uniformly successful.
As a shameless self-promotion plug, check out PolarCOM
Polar Navy for your NMEA processing needs
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