First class medical is good for checking if you are able of holding it, but if you can pass the rest and have vision uncorrected or uncorrected to 20/20 then you can obtain a First class, especially if you are under 40. Second class expires after 12 months, if you get it at the beginning of 102, I am going to assume it is going to take longer then 12 months to wrap up 325. You would be left with a Third class anyway. 
 
Where I took my medical they charged more for the Second class then the Third and subsequently more then either for the First. I just opted for the Third since I knew I could get the Second. If you know you can pass a second class medical or first just get the third class since you will have to get a new medical later on anyway...second class for 325 as Farva mentioned. 
 
Thanks for bringing that to my attention by the way, I should be starting 325 in the Fall, so I guess I'm going to have to go in for another medical.