How hard is it to change ratios in an 8-3/4"?

Right now I have 3.73:1 Dana Power-Lock positraction innards, and man! does the engine ever rev high on the freeway! I had that ratio installed because I intended to go to the strip, but so far I haven't got the car sorted out well enough to do that, so I've been daily driving it.

I'd like to buy and install a non-posi 2.76:1 ring and pinion just for highway use, but I really have no idea about how to install it! Would you guys please take pity on me and tell me, just briefly and in general terms, what is involved in switching ratios?

Should I buy a fully pre-assembled 2.76 one-legger center section? Would I then be able to easily swap center sections if/when I ever decide to get some time slips? Again, I apologize for my ignorance. Thanks very much.