Hi,
I'm assuming that you are comfortable with OSPF configuration and are just asking for some ideas on how to migrate from EIGRP to OSPF. That is, I'm assuming you have an area design etc in mind.
One possible strategy is to start off with OSPF configured with an admin distance of say, 250. In fact, anything over 170 should be fine. What that would do is to make sure that any OSPF-learned routes are not installed in the routing table in preference to EIGRP.
I would then configure OSPF on one router at a time until all were done. Since you have configured a high AD for OSFP, you should find that no OSPF routes are present in the routing tables. However, you should be able to see all relevant LSAs in the OSPF database to verify that OSPF is indeed working okay.
Once you are happy with that, you can start reducing the AD for OSPF on your routers one by one until all of them are done. The native OSPF AD is higher than that of EIGRP so you can increase the EIGRP AD instead of lowering the OSPF AD (or do both).
The process is a bit more involved than what I've described above but this can form a starting point.
Hope that helps - pls rate the post if it does.
Paresh
