I think he ment that a person that want to use his offer sends the scene and the meshes to him and he opens the scene and starts rendering it.
Wel your demands proberly can't be set like you want.
1. it's gotta be in relativley small packages, let's say under 50 mb
That is no problem to do.
2. i want to be able to see what's being rendered, so i can check i'm not rendering anything wrong
Wel i am not sure about that, but Lightwave has a preview window when rending animations and still images dunno about other programs.( they proberly also have it ).
3. it's gotta be a very stable proggram
That depends on the hardware you are using and programs you are running while rendering. And no rendering program is very stable. But like i said that depends on hardware and your compuer configurations. So on one PC it's more stable then another.
4. i want to be able to do some work (text editing, checking HLP, etc) while the rendering is going on.
That also depends on how complex the scene is. If some one used Volumetrics then it wil be prety CPU intensive. And since you only have 192MB of ram it wil proberly be a pain to browse or run anything els in the background.
I think you shoudl carefully consider if you realy want to do this imo. But thats up to you.

The offer is nice, but i won't use it .See below:)
OS: Winxp Professional
Amd Athlon 1.2ghz
40gb ATA100 Maxtor HDD
Asus A7133 (if i remember the number corecly:p)
Geforce2 MX100/200 32MB APG
512MB SDRam pc-133