This mission is a tough one and no mistake. I beat it on about the 4th try (but if you ever saw me play, you'd know I got lucky

) Anyway, If I remember, you can drop 2 mechs. I would go for a Shadowcat for me and give my wingman a Catapult. Load that Catapult up with (if you have them) Clan LRMs and then give it a sensible energy weapons mix (this may only be a couple of ER mediums). Load the Shadowcat up to suit you. I haven't played Vengeance in years (not since it broke my computer) but I seem to recall that a Clan LBX AC 20 with an extra ton of ammo, 2 ER mediums and a Streak 6 SRM pack is an old classic loadout as far as I'm concerned.
As to the mission, do not be afraid to scout ahead and don't be afraid to take on bigger mechs than you (spot the Raven pilot.....). The convoy will follow the road to a bridge so you know where it's going. (I think shift - M will bring up your map) and try and keep some of your weapons intact. You have to blow the bridge at the end and I can tell you through bitter experience that it takes ages with 1 medium laser. Also, don't worry too much about your wingman. All that will happen is you'll lose their mech (I don't think the characters can die). You will get better mechs that a Catapult fairly soon (like the Madcat, 75 tons of yummy goodness and a heavier missile payload than the 'Pult along with the capacity to mount PPC's and medium autocannon or 6 ER Large Lasers (AKA ye Olde Laserwhore, very hot but very effective), just no Jump Jets, no loss to me or the Vulture, 60 tons of Clan beastliness with way better slots than the Catapult - performs essentially the same task but better, can mout 5 CLRM 20 if you can fiddle it comfortably as opposed to the Catapult's 3) so don't worry too much about preserving it.