The Democrat Mahoney is very well-funded and this would've been a highly competitive race even versus a scandal-less Foley if Foley hadn't been super well-funded. I think it's a very tough hold, but a lot depends on whether Foley's name gets replaced and who it is that replaces him. I do not think a "generic Republican" can hold this seat this year in much the same way that Thelma Drake held VA-02 in 2004.
It appears that they can field a replacement, but Foley's name will remain on the ballot:
http://www.nytimes.com/cq/2006/09/29/cq_1530.html