I agree.
It really doesn't make much sense to use a precious resource like a 1st rounder on an RB if yours is serviceable. It's not clear how much of an upgrade Lynch would be in his first year over McGahee, anyway. And if the line can't block, you can put Thurman back there and he wouldn't reach 1000 yards.
If McGahee is a goner, take a shot on a possible replacement in the 2nd or 3rd rounds, where plenty of talent at RB can still be found. Or, better, draft a RB next year, when he goes to Miami or wherever. But by all means fix the OL, DL, and MLB (since Fletch will leave) this year. That's what this team needs to win NOW.
Not another RB or WR - it's the sexy/Donahoe pic to fill the seats in the begining of the season, only to see them empty later on, since the OL can't block and the DL can't stop the run. The first three picks this year should go to the lines and MLB.