My logic is in line with Philvo's -- assuming you're doing the work yourself. The part is $12, the allignment is $50. So if you only replace one, then get it alligned, you spent $62. 6 months down the road, the other side is gonna go bad. So you'll spend another $12, and your allignment will need to be re-done -- another $50. For a grand total of $124 vs $74.
If it was me (and a year ago, it was me) and I was planning on holding on to the car, I'd do both the inner and outer tie-rod ends, and the ball joints all at once-- then get it alligned. That way, you should be all set for another 100K+ miles. (as long as your bushings are OK)

Jeff Pierce
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'93 945 Turbo ( one kickass family car ! ), '92 Mercedes 190E (my daily driver), '53 Willys-Overland Pickup (my snow-plow truck/conversation piece)