I often think it helps to divide a trade up by position and see how you end up in the end by looking at respective players individually:
So MY breakdown would be something along the lines of
1. Tejada for Garciaparra
As far as Nomar, there's not really any replacing him. However, if you had to choose a SS to replace him behind Jeter and A-Rod, I think Tejada would be one along with my man, Jimmy Rollins.
2. Helton for Konerko: With all due respect to Paul, this one is a gimme. So valuable, especially with that ballpark and that smooth swing.
3. Shea Hillendbrand for Adam Dunn: I think this part is a no go for you. Hillenbrand has proved he can play in this league and plays for a pennant contender which increases opportunity. While the Reds are a strong hitting club, I think a lack of playing time is going to affect his numbers--------------> interesting note: Gammons was talking about how the Phils should trade Rolen to Cincy for Casey and Sullivan (or anybody else in that awesome bullpen). That would allow Dunn to play 1st on a daily basis
4. Rivera for Guardado: I like Eddie a lot. His ERA and WHIP are indicative of a strong performance this year. However, Mariano still wins out because that cut fastball is just sooooo nasty.
5. Lastly, Mesa and Perez for D. Lowe: I don't know what to say about this one. Derek has long surpassed expectation and the interesting thing is he's being consistent as well. Perez is no pushover and still puts up respectable numbers. Plus, Mesa might make this one a push.
Trades with multiple players are always tricky. As far as this trade is concerned. if saves are a concern and you can find a suitable replacement at 3B, then I would highly consider taking this trade. If it's the opposite (ESPECIALLY finding someone to replace Hillenbrand), I would highly consider NOT taking this trade.
So, just some ideas you may want to consider