Upgrading Drupal

hi
it is the first time i upgrade drupal site. when i did it on my local machine all went well but when upgrading on the site on the server for now i see some problem:

Hi,
What will happen with CCK fields on D7 if I try to upgrade from D6?

I have 2 Drupal sites that are long overdue for upgrading. One is on Drupal 6.13 and the other is 6.16. Does anybody know if there are any known problems or new requirements when making this leap? A year ago I upgraded my 6.15 site to 6.16 and it broke because of some kind of PHP change but was fixable the next day via a config file modification. The version of PHP on my servers are 5.2.17 and MySQL is 5.0.91. My 6.13 site is hosted on GoDaddy and my 6.16 site is on 1&1 if that matters.

Thanks

I have frequently moved Drupal sites around from host to host by simply doing a db export/import and tar'ing / untar'ing the /sites directory. However, I am having real trouble with one particular site. I had a development site at hostname-dev.domain and moved it to hostname.domain.

Can I upgrade drupal from 7.0 straight to 7.4 or do I need to do it incrementally like 7.0->7.1->7.2->7.3->7.4?

I seemed to upgrade fine, after migrating I started the process of updating some of the modules. I must have made the mistake up updating too many at once. Ubercart along with a few others. I got the php memory error which I have seen before. I bumped up the memory limit in my php.ini to 256 MB. Now when I try to load the website, I just get the connecting title and the tab just spins (sorry for the untechnical jargon). Basically the site will not load and it just attempts to connect indefinitely. Is there anything I can do short of starting over?