I am still struggling with getting my pin header install to work. Sounds like you will need to suck the old solder out first. You WILL need to solder a d0 point either way. I highly recommend getting an old electrical circuit board with small solder points and practise practise. Whatever board you get you can bet the xbox solder points are smaller.
I lifted a trace on my first install, had to solder a wire from both ends of the trace that i broke. Now i can solder very well and can offer this advice. Use a 15-20W soldering iron with a VERY fine tip. Clean your solder point with a cleaning solution first. Use flux to solder. Make sure your solder head is wet. Make sure your confident soldering small before you start on your precious box. The technique i learnt from trial and error is prob not orthodox but it is effective.