SAP has a OS/DB migrations guide/checklist and a go-live check that has to be performed before you go live on the new system. I have done this several time for different DB and OS. Seeing that this will be a hetrogenius migration you can run the R/3 Inst. on the DEV system and export the DB. Run the install on the new DEV system and then have your functional team leads go thought the system and do a check of the interfaces. One thing to remember, if you had any custom development work done in your system and the ADAP guys wrote the SQL queries in native SQL and not Open SQL you will have to re-write that code. If you have any other questions please let me know.
Hope this helps.