I have Cingular and I want to switch from my old ericsson to a used Nextel i530 off ebay.
Can I do this myself? How much would it cost for someone to do this for me? Does it need to be unlocked? Will it work?

Frankly put..

It is impossible to do...

The i530 uses a technology called iDEN, whereas the Cingular network is GSM...

You can unlock the i530, but it will still not work with the different network type that Cingluar has.

When you buy a phone from Ebay, you need to look at the Networks it will work on. 99.9% of the time Nextel phones will NOT work with any GSM provider (Cingular, AT&T, and Tmobile).

Yep, afraid so. Your old phone is a bit too old. All the new Cingular phones use the new GSM service. Whats nice about GSM phones is you can get almost any phone that accepts a SIM card and just move your service over into that phone. I took my sim card out of my Motorola T720 one day and dropped it in my buddys Motorola V600 and I was talking on it and whatnot to see how it compared to mine.

SIM technology is pretty handy when it comes to cell phones

We have only sim-technology here