Fix Wordpress Site/Server Issue: Spam and Hack (Security Issue)

We have 2 clients whom both have experienced some problems with their Wordpress based sites. It seems they were 'hacked' or some sort of security hole in the widgets or coding that allowed very separate incidences over past 3 weeks. The two websites are completely independent and unique (not on same server, not developed by same dev teams): Client Site #1: This particular client noticed that last week, their website started having 'spam ad pop-ups' occur when the visitors come to site, the contact forms seemed to have stopped working, and now the website is completely offline, with an 'Internal Server Error' message when you attempt to visit the site. For THIS client, we must a) Restore site, b) Get 'Contact Forms' working/functioning appropriately again, and C) ENSURE this problem will not re-occur/happen again and secure the website. Client Site #2: Client noticed about 4 weeks ago, that the website began attempting to spam and send spam e-mails randomly. Some sort of bug or glitch infected the site (we suspect through some widget vulnerability), and caused a bunch of e-mail server traffic issues (in addition to heavily spamming others through the site and CMS). Since then, we have restored the website to an older version/restore point, however, we still want to investigate the problem and ensure to client it won't occur again, and that the problem/security hole or bot/virus that caused the problem is permanently corrected. For someone with experience in this area, and well versed in fixing crashed websites and debugging security problems, widget holes, spam and spamming bots on WP sites, etc. this should be a very quick and straight forward project. We would like to complete it in FULL tomorrow and have both sites back to online and functioning by the end of the day tomorrow (within 30 hours of job posting). I do not yet want to share the domains/access to clients sites until we once prospect a potential candidate, at which point, we will share the domains and any logs/insight on the problem and login access to investigate. DO NOT simply send a message (generic, copy paste message) what simply is a copy/paste of your Wordpress experience. We want to hear specifically about your experience in fixing Wordpress websites that have gone down, encountered security issues, and have vast experience in finding, fixing, and protecting websites. We want both to be functioning without either or any of the issues, but more than that: We want to feel 100% safe it is a permanent fix and that we won't encounter the same problem or error again.