OK, here's the deal. I know I am repeating what has already been said by IIP but here goes. If you have a 5-lnb dish, when you are tuned to a 99/101 channel the guide comes from 101. When you are tuned to a 103/110/119 channel the guide comes from 119. Telling the receiver that you have a Slimline 3 will NOT, repeat NOT change that. It will remove the 110/119 channels from the guide but when you are tuned to a channel on 103 the receiver will still expect the guide to come from 119. So unless you use an SWM, or use the workaround described below, you will lose guide data if you spend most of your time watching a channel off 103 (like most HD).
The slimline 3 gets over this problem as IIP says by having a different stack plan so the 101 guide data comes down to the receiver even if you are tuned to a 103 channel. You can't make a Slimline 5 behave like a Slimline 3.
If you have an SWM8 or an SWM LNB then the SWM automatically delivers the guide from 101 whichever satellite you are tuned to, so the lack of 119 is not a problem with SWM.
The workaround has been posted many times but I will post it again. You have to get the receiver, or tuner 1 of the DVR, onto a 101 channel regularly to avoid the guide data problem. Fo the receiver it's easy. Set a daily autotune for a 101 channel (like BBCA) for early in the morning (maybe 3am). When you wake up in the morning the receiver will still be tuned to BBCA and the guide will have been refreshed.
For the DVR it's more complex. The guide is only processed by tuner 1 so you have to make sure that tuner is on a 101 channel. To do that you have to set up two simultaneous short manual recordings on 101 channels for the same time each early morning, that is the only way to make sure that tuner 1 is set to a 101 channel.
And we should not call the Slimline 3 the 3-lnb dish, the 3-lnb dish is the old oval one! Slimline 3 or SL3 will avoid confusion.