how can I do this
 

is there a sql script I can run to say change forum id 48 to forum id 1?

nope there isn't as it's something which is not really needed

if you want to do so you have to run a lot of queries:

[sql]UPDATE table SET forumid = 1 WHERE forumid = 48[/sql] for every table which has a forumid field.

not that you ahve to update all caches as well afterwards, so i'd advice you not to do so

Why do you want to do this?

for some reason my main category is id 48 instead of 1 and if I add a forum as parent to this it adds it as a sub forum instead of forum within category

The id is just an internal number. It doesn't matter what the id of your main category is.

so why won't my forums add into the categories like they should but instead go into subforum

Then you didn't set the correct Parent.