It cost me about the same to replace my amalgalms with composite; if you do have fillings in root canaled teeth I would not bother do any work on them besides tooth extraction. Why do you require crowns? For badly damaged teeth filled with amalgams?
Some people feel better after Amalgam removal, some feel the same, some feel worse; its dependent on how good of a job the dentist did, how sensitive you are to mercury among other things, so its kind of a gambling to have dental work performed before a major trip. If you do go ahead with the dental work you can stock up on chelation supps before the trip (if dentist finds chelation necessary).
If you remove your root canaled teeth it will take at least 3 months before they can place a bridge.
I had 2 teeth removed about 2 months ago but one extraction is giving me problems because on the roots was connected to sinus so its taking a while to close up properly (needed Antibiotics because of my blocked sinuses).
Unfortunately Im looking at the same ballpark figure to do all my dental work; I went ahead and remove root canaled teeth even if I can afford the bridges for a long while.