What is the best say to transfer data between 2 different versions of SugarCRM?

[endergonic]

Looking for some guidance with migrating/transferring data(Accounts & Leads) from SugarCRM CE Version 5.5.0a (Build 6659) to fresh instance of SugarCRM CE Version 6.1.3 (Build 5640).

I was going to export the accounts/leads from old instance and import to new. (I'm thinking there is an easier way, i'm all ears) Below is what I am having issues with.

List of Challenges
Accounts with Attachments [No export/import that I can see, you could create script to match hash ID with filename but how do you link to appropriate account in new instance without manually doing it?]

Mapping ID fields for users between the 2 instances [is there an easier way then excel and find + replace?]

[Angel]

Assuming you have direct access to the file system and database server, your easiest option would be to use something like Talend.

With Talend, you'll be able to easily transfer data from one server to the other and the attachments could easily be handled by simply copying the cache/upload folder from the old server to the new one.