I think that anybody who calls himself/herself a "linux-dummy" should begin with the most widely used distribution, because it will probably also be the most tested (so hopefully the least buggy) and it will be the easiest to find (how-to) guides for such a distribution.

So I would recommend to use 32bit Ubuntu 11.04 or a ubuntu derivative like Linux Mint 11 (32bit).

This version can also use more then 4GB ram, so for that you do not need the 64bit version. In fact I think the 64bit version will give new-users more problems than advantages. Also in the next Ubuntu there will be some significant changes in the way the 64bit version handles 32bit libraries and software. So if you really want to use 64bit, use the 32bit version of 11.04 for now, and upgrade to the 64bit version of Ubuntu 11.10 when it becomes available.