Its actually not to bad of a job, to do, but it is an expensive endeavor. I was able to source a blank plate that fit into the stock cluster holder. The gauges them selves can get expensive if you want quality gauges (I went with Speedhut which are top notch). Some of the reasons mine was expensive was:
1. I wanted it plug and play with the ability to go back to the stock gauge - this required a special connectors
2. I wanted a GPS speedo - which in itself is more expense than a normal speedo, and requires you to buy a few parts to enable the signal to still be sent to the ECU from the transmission
3. I wanted boost/oil/fuel pressure gauges in my unit, but didn't want mechanical pressures lines so I had to spend more on sending units
4. Wanted a scan master in there - had to buy the scan master G
All this started to add up, I think it was in it 1500 bucks, but you could do it probably for around 800 with fewer gauges and options.