I take it you realise that anyone who responds is only guessing ...
I'm going to guess that the vehicle has the XL-7 transmission fitted, and that it's an automatic transmission, because manual transmission XL-7s can be difficult to find - if I'm right on that, the answer to the first question is NO, and the second is MAYBE
The Geo speedometer is cable driven and the XL-7 transmission doesn't have a cable output - in theory you could remove the speed sensor off of the transfer case and fit the one off of the Geo, but you'd probably need to get into the transfer case and fiddle with the drive gears to get them to mesh properly - I've never heard of anyone doing it, but you could give it a shot. In theory, if it's an automatic, you could swap the transfer case from one transmission to the next, but again, I've never heard of this being done. Regarding the temperature gauge, it depends on the year of the H27 donor, on later models the coolant temperature sensor did not drive the temperature gauge directly, but routed the signal through the BCM (body control module), the Geo temperature gauge was designed to be driven directly from the sensor, and it needs to be a "matching" sensor for it to work properly.
Continuing my guessing game - if it is an automatic, any sloppiness in the shifter is likely to in the shifter itself, this generation of automatics uses a cable operated shifter, so if you have a sloppy Geo shifter, the XL-7 shifter MAYBE in better condition.
Now if I guessed incorrectly my answers MAY also be incorrect - I assumed the XL-7 transmission would be used for a number of reasons - starting with ease of mating the bellhousing to the engine and knowing that swapping the transmission with the engine typically requires little more than custom driveshafts, which is relatively easy to do.
Personally I would hesitate to buy anyone's "incomplete project", especially one as complex as this, unless I had first hand knowledge of what had been done - little details can make or break the swap - the year XL-7 the H27 came out of determines the complexity of the electronics, which are only important if you're going to use the original ECU to fuel the engine, if it's an automatic then you need to figure out how to shift the automatic, assuming you stick with the automatic out of the XL-7 which, depending on the market could be a four speed or five speed, if it's a manual, an after-market ECU might be easier that sorting out the XL-7 electronics, assuming you have the skills to install and tune it.
All in all, you're asking us questions after giving us very little detail, and so forcing us to make assumptions and guesses.