Maybe you should just look at the BASIC stamp...it's designed for beginner hobbiests and all you would really need to do is connect power to the sensors, and LCDs and then connect their signal wire to the BASIC stamp.
Start first with reading temperature...then add on an LCD...then add on a temperature sensor. Test it everytime you attached something new. Use a debug program to make sure it's reading the sensor right (until you get the LCD attached then you can read it off that). Once you manage to read the temperature properly it should start to become much more clear. Read up on some of the datasheets and manuals first. It may take 20 reads before you start to get it, but hey, that's what it takes.
(Do you know how to code?) Try this first, get a BASIC stamp and a carrier board, then find an ADC pin (get any one, it doesn't matter).
Then get one of these:
http://www.sparkfun.com/commerce/product_info.php?products_id=251
http://www.sparkfun.com/commerce/product_info.php?products_id=306
One is the thermocouple wire, and one is the IC to signal condition the thermocouple wire. It will output an analog voltage. You just take this pin and connect it straight to an ADC pin on the basic stamp. (Remember to google up some stuff about thermocouples so you understand how they works). You then just code the basic stamp (you have to figure this out for yourself since I don't know basic) to read the ADC's voltage. If you can get that done, you should have a much clearer idea of what you need to do.
Read the datasheets and at your point, pay particular attention to the pin names and what they do. Also, in the AD595 datasheet, it has some nice pictures around the end giving a basic explanation about how it works too. Datasheets...always read the datasheets carefully and several times if required.
There is nothing like getting your feet wet, because even if things go wrong, at least then you will KNOW what you do not know. At this point, you're probably not even sure if you know something or not. Start with a temperature sensor project to get a feel for it. After you get that then add the LCD and pressure gauge. Read the BASIC stamp stuff if you decide to go this route...LOTS of tutorials. You shouldn't have any insurmountable problems.
A thermocouple are two wires of different metals that have some properties to produce a voltage difference between each end if there is a temperature gradient along the wire, therefore a thermocouple measures a voltage difference, not an absolute voltage. So it means if you know the temperature at "your" end of the wire and voltage difference, then you can figure out the temperature at the other end. Rather than keeping the temperature at "your" end at a fixed temperature (difficult to do) what the IC does it it uses an internal silicon temperature sensor to measure the temperature at your end and then takes the voltage from the thermocouple and uses these to output a voltage proportional to the temperature. What you have to keep in mind is to make sure you have a temperature gradient across the thermocouple, so you don't want a short wire and you want to make the temperature difference between the ends of the wires at great as possible (far away from each other). A
The thermocouple effect happens whenever two metals are in contact and there is a temperature gradient, but you can usually ignore this effect when things are very close together because then they are at the same temperature. Around the IC, metals other than the thermocouple wire metals come into contact with each other, and these junctions would create thermocouples too, but because they are so close together the temperature-dependent voltages added into the thermocouple voltage are neglible (remember, no temperature gradient, no voltage produced). This last paragraph is just something that took me a while to realize so I stuck it in...I was concerned about the thermocouple metals touching the copper traces on the PCB and skewing the voltage readings.
So yeah...that's just a quickie explanation.
If you still have no idea about what uC to pick, maybe this or this BASIC stamp board:
**broken link removed**
You can also get LCD screens from the same company (presumably designed to work with these units which would make things easier).
Or one of these if you prefer C or Java "like" language (this is the first uC I started on, and it was DEAD easy. Hardest part was hunting around the manual to look for functions during coding):
http://www.oopic.com/oopicr.htm
It's within your ability! Believe in yourself! Good luck!