What computer/monitor is best for a beginner photo editor?

I am currently doing my PP on a Dell laptop with an i5 processor and a screen resolution of 1366 x 768.  Is this a reasonable set-up for PP or am I going to see a significant difference if I connect a good external monitor to my laptop?  I cannot afford a new PC at the moment and my laptop is just a few months old so it is out of the question to buy a while new system at this point.